Build a food chain. Methodical development on the world around (Grade 3) on the topic: "Who is what? Food chains"
Food or trophic chain called the relationship between different groups of organisms (plants, fungi, animals and microbes), in which energy is transported as a result of eating some individuals by others. Energy transfer is the basis for the normal functioning of an ecosystem. Surely these concepts are familiar to you from the 9th grade of the school from the general biology course.
Individuals of the next link eat the organisms of the previous link, and this is how matter and energy are transported along the chain. This sequence of processes underlies the living cycle of substances in nature. It is worth saying that a huge part of the potential energy (about 85%) is lost during the transfer from one link to another, it dissipates, that is, it is dissipated in the form of heat. This factor is limiting in relation to the length of food chains, which in nature usually have 4-5 links.
Types of food relationships
Within ecosystems, organic matter is produced by autotrophs (producers). Plants, in turn, are eaten by herbivorous animals (first-order consumers), which are then eaten by carnivores (second-order consumers). This 3-link food chain is an example of a proper food chain.
Distinguish:
pasture chains
Trophic chains begin with auto- or chemotrophs (producers) and include heterotrophs in the form of consumers of various orders. Such food chains widespread in land and marine ecosystems. They can be drawn and compiled in the form of a diagram:
Producers —> Consumers of the 1st order —> Consumers of the 1st order —> Consumers of the 3rd order.
A typical example is the grassland food chain (this can be both a forest zone and a desert, in which case only species various participants trophic chain and branching of the network of food interactions).
So, with the help of the energy of the Sun, a flower produces nutrients for itself, that is, it is a producer and the first link in the chain. A butterfly that feeds on the nectar of this flower is a consumer of the first order and the second link. The frog, which also lives in the meadow and is an insectivorous animal, eats a butterfly - the third link in the chain, a consumer of the second order. The frog is swallowed already - the fourth link and the consumer of the III order, the hawk is eaten by the snake - the consumer of the IV order and the fifth, as a rule, the last link in food chain. A person can also be present in this chain as a consumer.
In the waters of the World Ocean, autotrophs, represented by unicellular algae, can exist only as long as it is able to penetrate through the water column. sunlight. This is a depth of 150-200 meters. Heterotrophs can also live in deeper layers, rising to the surface at night to feed on algae, and in the morning again leaving to the usual depth, while making vertical migrations up to 1 km per day. In turn, heterotrophs, which are consumers of subsequent orders, living even deeper, in the morning rise to the level of habitation of consumers of the first order in order to feed on them.
Thus, we see that in deep water bodies, as a rule, seas and oceans, there is such a thing as a “food ladder”. Its meaning lies in the fact that organic substances that are created by algae in the surface layers of the earth are transferred along the food chain to the very bottom. Given this fact, the opinion of some ecologists that the entire reservoir can be considered a single biogeocenosis can be considered reasonable.
Detrital trophic relationships
To understand what a detrital food chain is, you need to start with the very concept of “detritus”. Detritus is a collection of the remains of dead plants, corpses and end products of animal metabolism.
Detrital chains are typical for communities of inland waters, the bottom of lakes with great depth, and oceans, many of whose representatives feed on detritus formed by the remains of dead organisms from the upper layers or accidentally falling into a reservoir from ecological systems located on land, in the form, for example , leaf litter.
The bottom ecological systems of the oceans and seas, where there are no producers due to the lack of sunlight, can only exist at the expense of detritus, the total mass of which in the World Ocean is over calendar year can reach hundreds of millions of tons.
Also, detrital chains are common in forests, where a considerable part of the annual increase in the biomass of producers cannot be eaten directly by the first link of consumers. Therefore, it dies off, forming litter, which, in turn, is decomposed by saprotrophs, and then mineralized by decomposers. Fungi play an important role in the formation of detritus in forest communities.
Heterotrophs that feed directly on detritus are detritivores. In ground ecological systems detritophages include some types of arthropods, in particular insects, as well as annelids. Large detritus feeders among birds (vultures, crows) and mammals (hyenas) are usually called scavengers.
In the ecological systems of waters, the bulk of detritus feeders are aquatic insects and their larvae, as well as some representatives of crustaceans. Detritophages can serve as food for larger heterotrophs, which, in turn, can later become food for higher-order consumers.
The links in the food chain are also called trophic levels. By definition, this is a group of organisms that occupies a specific place in the food chain and represents a source of energy for each of the subsequent levels - food.
organisms I trophic level in pasture food chains are primary producers, autotrophs, that is, plants, and chemotrophs - bacteria that use energy chemical reactions for the synthesis of organic substances. In detrital systems, autotrophs are absent, and trophic level I of the detrital trophic chain forms detritus itself.
Last, V trophic level represented by organisms that consume dead organic matter and end products of decay. These organisms are called destructors or decomposers. Decomposers are mainly represented by invertebrates that are necro-, sapro- and coprophages, using remains, waste and dead organic matter as food. This group also includes saprophage plants that decompose leaf litter.
The level of destructors also includes heterotrophic microorganisms capable of converting organic substances into inorganic (mineral) ones, forming the final products - carbon dioxide and water, which return to the ecological system and re-enter the natural cycle of substances.
The Importance of Nutritional Relationships
Most living organisms eat organic food, this is the specificity of their life on our planet. Among this food are plants, and the meat of other animals, their products of activity and dead matter, ready for decomposition. The very process of nutrition in different species of plants and animals occurs in different ways, but the so-called They are always formed, they transform matter and energy, and nutrients can thus pass from one creature to another, carrying out the circulation of substances in nature.
in the forest
Forests of various kinds cover quite a lot of land surface. It is the lungs and the instrument of cleansing our planet. It is not for nothing that many progressive modern scientists and activists oppose mass felling forests. The food chain in the forest can be quite diverse, but, as a rule, includes no more than 3-5 links. In order to understand the essence of the issue, let us turn to the possible components of this chain.
Producers and consumers
- The first are autotrophic organisms that feed on inorganic food. They take energy and matter to create their own bodies, using gases and salts from their environment. An example is green plants that get their nutrition from sunlight through photosynthesis. Or numerous types of microorganisms that live everywhere: in the air, in the soil, in the water. It is the producers that for the most part make up the first link in almost any food chain in the forest (examples will be given below).
- The second are heterotrophic organisms that feed on organic matter. Among them are those of the first order that directly carry out nutrition at the expense of plants and bacteria, producers. The second order - those who eat animal food (predators or carnivores).
Plants
As a rule, the food chain in the forest begins with them. They are the first link in this cycle. Trees and shrubs, grasses and mosses obtain food from inorganic substances using sunlight, gases and minerals. A food chain in a forest, for example, may begin with a birch tree, the bark of which is eaten by a hare, who, in turn, is killed and eaten by a wolf.
herbivorous animals
In various forests, animals are found in abundance that feed on plant food. Of course, for example, it is very different in its content from the land middle lane. They live in the jungle different kinds animals, many of which are herbivores, which means they make up the second link in the food chain, eating plant foods. From elephants and rhinos to barely visible insects, from amphibians and birds to mammals. So, in Brazil, for example, there are more than 700 species of butterflies, almost all of them are herbivores.
Poorer, of course, is the fauna in the forest belt of central Russia. Accordingly, there are much fewer options for the supply chain. Squirrels and hares, other rodents, deer and elk, hares - this is the basis for such chains.
Predators or carnivores
They are called so because they eat flesh, eating the meat of other animals. They occupy a dominant position in the food chain, often being the final link. In our forests, these are foxes and wolves, owls and eagles, sometimes bears (but in general they belong to which they can eat both plant and animal food). In the food chain, both one and several predators can take part, eating each other. The final link, as a rule, is the largest and most powerful carnivore. In the forest of the middle lane, this role can be played, for example, by a wolf. There are not too many such predators, and their population is limited by the food base and energy reserves. Since, according to the law of conservation of energy, when nutrients pass from one link to the next, up to 90% of the resource can be lost. This is probably why the number of links in most food chains cannot exceed five.
Scavengers
They feed on the remains of other organisms. Oddly enough, there are also quite a lot of them in the nature of the forest: from microorganisms and insects to birds and mammals. Many beetles, for example, use the corpses of other insects and even vertebrates as food. And bacteria are able to decompose the dead bodies of mammals in a fairly short time. Scavenging organisms play a huge role in nature. They destroy matter, transforming it into inorganic substances, release energy, using it for their life activity. If it were not for scavengers, then, probably, the entire earthly space would be covered with the bodies of animals and plants that have died for all time.
in the forest
To make a food chain in the forest, you need to know about those inhabitants who live there. And also about what these animals can eat.
- Birch bark - insect larvae - small birds - birds of prey.
- Fallen leaves - bacteria.
- Butterfly caterpillar - mouse - snake - hedgehog - fox.
- Acorn - mouse - fox.
- Cereals - mouse - eagle owl.
There are also more authentic ones: fallen leaves - bacteria - earthworms - mice - mole - hedgehog - fox - wolf. But, as a rule, the number of links is not more than five. The food chain in a spruce forest is slightly different from that in a deciduous forest.
- Cereal seeds - sparrow - wild cat.
- Flowers (nectar) - butterfly - frog - already.
- Fir cone - woodpecker - eagle.
Food chains can sometimes intertwine with each other, forming more complex, multi-level structures that combine into a single forest ecosystem. For example, the fox does not disdain to eat both insects and their larvae, and mammals, so several food chains intersect.
In nature, any species, population, and even a single individual do not live in isolation from each other and their environment, but, on the contrary, experience numerous mutual influences. Biotic communities or biocenoses - communities of interacting living organisms, which are a stable system connected by numerous internal connections, with a relatively constant structure and an interdependent set of species.
Biocenosis is characterized by certain structures: species, spatial and trophic.
The organic components of the biocenosis are inextricably linked with the inorganic ones - soil, moisture, atmosphere, forming together with them a stable ecosystem - biogeocenosis .
Biogenocenosis- a self-regulating ecological system formed by living together and interacting with each other and with inanimate nature, populations of different species in relatively homogeneous environmental conditions.
Ecological systems
Functional systems that include communities of living organisms of different species and their habitats. The connections between the components of the ecosystem arise, first of all, on the basis of food relationships and ways of obtaining energy.
Ecosystem
A set of species of plants, animals, fungi, microorganisms interacting with each other and with the environment in such a way that such a community can be preserved and function for an indefinitely long time. Biotic community (biocenosis) consists of a community of plants ( phytocenosis), animals ( zoocenosis), microorganisms ( microbiocenosis).
All organisms of the Earth and their habitat also represent an ecosystem of the highest rank - biosphere , which has stability and other properties of the ecosystem.
The existence of an ecosystem is possible due to the constant influx of energy from the outside - such an energy source, as a rule, is the sun, although this is not true for all ecosystems. The stability of an ecosystem is ensured by direct and feedback links between its components, the internal circulation of substances and participation in global cycles.
The doctrine of biogeocenoses developed by V.N. Sukachev. The term " ecosystem"Introduced into use by the English geobotanist A. Tensley in 1935, the term" biogeocenosis"- Academician V.N. Sukachev in 1942 biogeocenosis must be present as the main link plant community(phytocenosis), which ensures the potential immortality of biogeocenosis due to the energy produced by plants. ecosystems may not contain phytocenosis.
Phytocenosis
A plant community that has historically developed as a result of a combination of interacting plants in a homogeneous area of a territory.
He is characterized:
- a certain species composition,
- life forms
- tiered (aboveground and underground),
- abundance (frequency of occurrence of species),
- accommodation,
- aspect (appearance),
- vitality
- seasonal changes,
- development (change of communities).
Layered (number of floors)
One of characteristic features plant community, which consists, as it were, in its floor-by-floor division both in the above-ground and in the underground space.
Aboveground layering allows better use of light, and underground - water and minerals. Usually, up to five tiers can be distinguished in the forest: the upper (first) - tall trees, the second - low trees, the third - shrubs, the fourth - herbs, the fifth - mosses.
Underground layering - a mirror reflection of the aboveground: the roots of trees go deepest of all, underground parts of mosses are located near the surface of the soil.
According to the method of obtaining and using nutrients All organisms are divided into autotrophs and heterotrophs. In nature, there is a continuous circulation of biogenic substances necessary for life. Chemical substances extracted by autotrophs environment and return to it through heterotrophs. This process takes on very complex forms. Each species uses only a part of the energy contained in organic matter, bringing its decay to a certain stage. Thus, in the process of evolution, ecological systems have developed chains And power supply .
Most biogeocenoses have a similar trophic structure. The basis of them are green plants - producers. Herbivorous and carnivorous animals are necessarily present: consumers of organic matter - consumers and destroyers of organic residues - decomposers.
The number of individuals in the food chain consistently decreases, the number of victims is greater than the number of their consumers, since in each link of the food chain, with each transfer of energy, 80-90% of it is lost, dissipating in the form of heat. Therefore, the number of links in the chain is limited (3-5).
Species diversity of biocenosis It is represented by all groups of organisms - producers, consumers and decomposers.
Any link broken in the food chain causes a violation of the biocenosis as a whole. For example, deforestation leads to a change species composition insects, birds, and, consequently, animals. On a treeless site, other food chains will develop and another biocenosis will form, which will take more than a dozen years.
Food chain (trophic or food )
Interrelated species that sequentially extract organic matter and energy from the original food substance; moreover, each previous link in the chain is food for the next one.
Food chains in each natural area with more or less homogeneous conditions of existence are composed of complexes of interconnected species that feed on each other and form a self-sustaining system in which the circulation of substances and energy is carried out.
Ecosystem components:
- Producers - autotrophic organisms (mainly green plants) are the only producers of organic matter on Earth. Energy-rich organic matter in the process of photosynthesis is synthesized from energy-poor inorganic substances (H 2 0 and CO 2).
- Consumers - herbivorous and carnivorous animals, consumers of organic matter. Consumers can be herbivores when they use producers directly, or carnivores when they feed on other animals. In the food chain, they most often have serial number from I to IV.
- decomposers - heterotrophic microorganisms (bacteria) and fungi - destroyers of organic residues, destructors. They are also called the orderlies of the Earth.
Trophic (food) level - a set of organisms united by the type of food. The idea of the trophic level allows us to understand the dynamics of energy flow in an ecosystem.
- the first trophic level is always occupied by producers (plants),
- the second - consumers of the first order (herbivorous animals),
- the third - consumers of the second order - predators that feed on herbivorous animals),
- the fourth - consumers of the III order (secondary predators).
Distinguish the following types food chains:
IN pasture chain (eating chains) green plants are the main source of food. For example: grass -> insects -> amphibians -> snakes -> birds of prey.
- detritus chains (decomposition chains) begin with detritus - dead biomass. For example: leaf litter -> earthworms-> bacteria. A feature of detrital chains is also that in them plant products are often not consumed directly by herbivorous animals, but die off and are mineralized by saprophytes. Detrital chains are also characteristic of ecosystems of the ocean depths, the inhabitants of which feed on dead organisms that have descended from the upper layers of the water.
Relationships between species in ecological systems that have developed in the process of evolution, in which many components feed on different objects and themselves serve as food for various members of the ecosystem. Simplified, the food web can be represented as intertwining food chains.
Organisms of different food chains that receive food through an equal number of links in these chains are on one trophic level. At the same time, different populations of the same species included in different food chains can be located on different trophic levels. The ratio of different trophic levels in an ecosystem can be represented graphically as ecological pyramid.
ecological pyramid
A way to graphically display the ratio of different trophic levels in an ecosystem - there are three types:
The abundance pyramid reflects the abundance of organisms at each trophic level;
The biomass pyramid reflects the biomass of each trophic level;
The energy pyramid shows the amount of energy that has passed through each trophic level in a given amount of time.
Ecological pyramid rule
A pattern that reflects a progressive decrease in the mass (energy, number of individuals) of each subsequent link in the food chain.
Pyramid of numbers
An ecological pyramid showing the number of individuals at each food level. The pyramid of numbers does not take into account the size and weight of individuals, life expectancy, metabolic rate, but the main trend is always traced - a decrease in the number of individuals from link to link. For example, in the steppe ecosystem, the number of individuals is distributed as follows: producers - 150000, herbivorous consumers - 20000, carnivorous consumers - 9000 ind./ar. The meadow biocenosis is characterized by the following number of individuals on an area of 4000 m 2: producers - 5,842,424, herbivorous consumers of the 1st order - 708,624, carnivorous consumers of the 2nd order - 35,490, carnivorous consumers of the 3rd order - 3.
Biomass pyramid
The pattern according to which the amount of plant matter that serves as the basis of the food chain (producers) is approximately 10 times greater than the mass of herbivores (consumers of the 1st order), and the mass of herbivores is 10 times greater than the mass of carnivores (consumers of the 2nd order), t i.e. each subsequent food level has a mass 10 times less than the previous one. On average, out of 1000 kg of plants, 100 kg of the body of herbivores is formed. Predators eating herbivores can build 10 kg of their biomass, secondary predators - 1 kg.
energy pyramid
expresses a pattern according to which the flow of energy gradually decreases and depreciates in the transition from link to link in the food chain. So, in the biocenosis of the lake, green plants - producers - create a biomass containing 295.3 kJ / cm 2, consumers of the first order, consuming plant biomass, create their own biomass containing 29.4 kJ / cm 2; consumers of the second order, using consumers of the first order for food, create their own biomass containing 5.46 kJ / cm 2. The loss of energy during the transition from consumers of the 1st order to consumers of the 2nd order, if they are warm-blooded animals, increases. This is explained by the fact that in these animals a lot of energy is spent not only on building their biomass, but also on maintaining a constant body temperature. If we compare the cultivation of a calf and a perch, then the same amount of food energy expended will give 7 kg of beef and only 1 kg of fish, since the calf feeds on grass, and the predatory perch feeds on fish.
Thus the first two types of pyramids have a number of significant drawbacks:
The biomass pyramid reflects the state of the ecosystem at the time of sampling and therefore shows the ratio of biomass in this moment and does not reflect the productivity of each trophic level (i.e., its ability to form biomass for a certain period of time). Therefore, when fast-growing species are among the producers, the biomass pyramid may turn upside down.
The energy pyramid allows you to compare the productivity of different trophic levels, since it takes into account the time factor. In addition, it takes into account the difference in the energy value of various substances (for example, 1 g of fat provides almost twice as much energy as 1 g of glucose). Therefore, the pyramid of energy always tapers upward and is never inverted.
Ecological plasticity
The degree of endurance of organisms or their communities (biocenoses) to the effects of environmental factors. Ecologically plastic species have a wide range of reaction rate , i.e., widely adapted to different habitats (stickleback and eel fish, some protozoa live in both fresh and salt waters). Highly specialized species can exist only in a certain environment: marine animals and algae - in salt water, river fish and plants lotus, water lily, duckweed live only in fresh water.
Generally ecosystem (biogeocenosis) characterized by the following indicators:
species diversity,
Density of species populations,
Biomass.
Biomass
The total amount of organic matter of all individuals of a biocenosis or species with energy contained in it. Biomass is usually expressed in units of mass in terms of dry matter per unit area or volume. Biomass can be defined separately for animals, plants, or certain types. So, the biomass of fungi in the soil is 0.05-0.35 t / ha, algae - 0.06-0.5, roots higher plants- 3.0-5.0, earthworms - 0.2-0.5, vertebrates - 0.001-0.015 t/ha.
In biogeocenoses there are primary and secondary biological productivity :
ü Primary biological productivity of biocenoses- the total total productivity of photosynthesis, which is the result of the activity of autotrophs - green plants, for example, Pine forest 20-30 years of age produces 37.8 t/ha of biomass per year.
ü Secondary biological productivity of biocenoses- the total total productivity of heterotrophic organisms (consumers), which is formed through the use of substances and energy accumulated by producers.
Populations. Structure and population dynamics.
Each species on Earth occupies a certain range because it can exist only under certain environmental conditions. However, living conditions within the range of one species can differ significantly, which leads to the disintegration of the species into elementary groups of individuals - populations.
population
A set of individuals of the same species occupying a separate territory within the range of the species (with relatively homogeneous habitat conditions), freely interbreeding with each other (having a common gene pool) and isolated from other populations of a given species, possessing all the necessary conditions to maintain their stability for a long time in changing environmental conditions. The most important characteristics populations are its structure (age, sex composition) and population dynamics.
Under the demographic structure populations understand its sex and age composition.
Spatial structure populations are the features of the distribution of individuals of a population in space.
Age structure population is related to the ratio of individuals of different ages in the population. Individuals of the same age are combined into cohorts - age groups.
IN age structure of plant populations allocate next periods:
Latent - the state of the seed;
Pregenerative (includes the states of a seedling, juvenile plant, immature and virginal plants);
Generative (usually divided into three sub-periods - young, mature and old generative individuals);
Post-generative (includes the states of subsenile, senile plants and the dying phase).
Belonging to a certain age state is determined by biological age- the degree of expression of certain morphological (for example, the degree of dissection of a complex leaf) and physiological (for example, the ability to give offspring) signs.
In animal populations, one can also distinguish various age stages. For example, insects that develop with complete metamorphosis go through the following stages:
larvae,
pupae,
Imago (adult insect).
The nature of the age structure of the populationdepends on the type of survival curve characteristic of a given population.
survival curvereflects the mortality rate in different age groups and is a declining line:
- If the mortality rate does not depend on the age of individuals, the death of individuals occurs in this type evenly, the death rate remains constant throughout life ( type I ). Such a survival curve is characteristic of species whose development occurs without metamorphosis with sufficient stability of the born offspring. This type is called type of hydra- it has a survival curve approaching a straight line.
- In species for which the role of external factors in mortality is small, the survival curve is characterized by a slight decrease until a certain age, after which there is a sharp drop due to natural (physiological) mortality ( type II ). The nature of the survival curve close to this type is characteristic of humans (although the human survival curve is somewhat flatter and is somewhere between types I and II). This type is called Drosophila type: this is what Drosophila demonstrates in laboratory conditions (not eaten by predators).
- Many species are characterized by high mortality on early stages ontogeny. In these species, the survival curve is characterized by sharp drop in the area of younger ages. Individuals that have survived the “critical” age demonstrate low mortality and survive to older ages. The type is named oyster type (type III ).
Sex structure populations
The sex ratio is directly related to the reproduction of the population and its sustainability.
There are primary, secondary and tertiary sex ratio in the population:
- Primary sex ratio determined by genetic mechanisms - the uniformity of the divergence of the sex chromosomes. For example, in humans, XY chromosomes determine the development of the male sex, and XX - the female. In this case, the primary sex ratio is 1:1, i.e., equally likely.
- Secondary sex ratio - this is the sex ratio at the time of birth (among newborns). It can differ significantly from the primary one for a number of reasons: the selectivity of eggs for spermatozoa carrying the X- or Y-chromosome, the unequal ability of such spermatozoa to fertilize, various external factors. For example, zoologists have described the effect of temperature on the secondary sex ratio in reptiles. A similar pattern is characteristic of some insects. So, in ants, fertilization is ensured at temperatures above 20 ° C, and at more low temperatures unfertilized eggs are laid. Males hatch from the latter, and mostly females from the fertilized ones.
- Tertiary sex ratio - sex ratio among adult animals.
Spatial structure populations reflects the nature of the distribution of individuals in space.
Allocate three main types of distribution of individuals in space:
- uniform or uniform(individuals are evenly distributed in space, at equal distances from each other); occurs rarely in nature and is most often caused by acute intraspecific competition (for example, in predatory fish);
- congregational or mosaic(“spotted”, individuals are located in isolated clusters); occurs much more frequently. It is associated with the characteristics of the microenvironment or the behavior of animals;
- random or diffuse(individuals are randomly distributed in space) - can be observed only in a homogeneous environment and only in species that do not show any desire to unite in groups (for example, in a beetle in flour).
Population size denoted by the letter N. The ratio of the increase N to the unit time dN / dt expressesinstantaneous speedchanges in population size, i.e. change in population at time t.Population Growthdepends on two factors - fertility and mortality, provided there is no emigration and immigration (such a population is called isolated). The difference between birth rate b and death rate d and isisolated population growth rate:
Population stability
This is its ability to be in a state of dynamic (i.e., mobile, changing) equilibrium with the environment: environmental conditions change - the population also changes. One of essential conditions sustainability is internal diversity. In relation to a population, these are mechanisms for maintaining a certain population density.
Allocate three types of dependence of population size on its density .
First type (I) - the most common, characterized by a decrease in population growth with an increase in its density, which is provided by various mechanisms. For example, many species of birds are characterized by a decrease in fertility (fertility) with an increase in population density; an increase in mortality, a decrease in the resistance of organisms with an increased population density; change in the age of onset of puberty depending on the density of the population.
The third type ( III ) characteristic of populations in which the “group effect” is noted, i.e. a certain optimal population density contributes to better survival, development, and vital activity of all individuals, which is inherent in most group and social animals. For example, for the resumption of populations of heterosexual animals, at least a density is needed that provides a sufficient probability of meeting a male and a female.
Thematic tasks
A1. Biogeocenosis is formed
1) plants and animals
2) animals and bacteria
3) plants, animals, bacteria
4) territory and organisms
A2. Consumers of organic matter in forest biogeocenosis are
1) spruce and birch
2) mushrooms and worms
3) hares and squirrels
4) bacteria and viruses
A3. The producers in the lake are
2) tadpoles
A4. The process of self-regulation in biogeocenosis affects
1) sex ratio in populations of different species
2) the number of mutations that occur in populations
3) predator-prey ratio
4) intraspecific competition
A5. One of the conditions for the sustainability of an ecosystem can be
1) her ability to change
2) variety of species
3) fluctuations in the number of species
4) the stability of the gene pool in populations
A6. Reducers are
2) lichens
4) ferns
A7. If the total mass received by a consumer of the 2nd order is 10 kg, then what was the total mass of producers that became a source of food for this consumer?
A8. Specify the detrital food chain
1) fly - spider - sparrow - bacteria
2) clover - hawk - bumblebee - mouse
3) rye - titmouse - cat - bacteria
4) mosquito - sparrow - hawk - worms
A9. The initial source of energy in the biocenosis is energy
1) organic compounds
2) inorganic compounds
4) chemosynthesis
1) hares
2) bees
3) blackbirds
4) wolves
A11. In one ecosystem you can find oak and
1) gopher
3) lark
4) blue cornflower
A12. Power networks are:
1) relationships between parents and offspring
2) family (genetic) ties
3) metabolism in the cells of the body
4) ways of transferring substances and energy in an ecosystem
A13. The ecological pyramid of numbers reflects:
1) the ratio of biomass at each trophic level
2) the ratio of the masses of an individual organism at different trophic levels
3) food chain structure
4) diversity of species at different trophic levels
Target: expand knowledge of biotic environmental factors.
Equipment: herbarium plants, stuffed chordates (fish, amphibians, reptiles, birds, mammals), insect collections, animal wet preparations, illustrations of various plants and animals.
Working process:
1. Use the equipment and make up two power circuits. Remember that a chain always starts with a producer and ends with a decomposer.
Plants → insects→lizard → bacteria
Plants → Grasshopper→ frog → bacteria
Recall your observations in nature and make two food chains. Sign producers, consumers (1st and 2nd orders), decomposers.
Violet → Springtails→predatory mites→carnivorous centipedes→ bacteria
Producer - consumer1 - consumer2 - consumer2 - decomposer
Cabbage→ slug→ frog →bacteria
Producer - consumer1 - consumer2 - decomposer
What is a food chain and what underlies it? What determines the stability of the biocenosis? Formulate a conclusion.
Output:
food (trophic) chain- rows of species of plants, animals, fungi and microorganisms that are related to each other by relationships: food - consumer (a sequence of organisms in which there is a phased transfer of matter and energy from source to consumer). Organisms of the next link eat the organisms of the previous link, and thus a chain transfer of energy and matter is carried out, which underlies the cycle of substances in nature. With each transfer from link to link, a large part (up to 80-90%) of the potential energy is lost, dissipating in the form of heat. For this reason, the number of links (species) in the food chain is limited and usually does not exceed 4-5. The stability of the biocenosis is determined by the diversity of its species composition. Producers- organisms capable of synthesizing organic substances from inorganic, that is, all autotrophs. Consumers- heterotrophs, organisms that consume ready-made organic substances created by autotrophs (producers). Unlike reducers
Consumers are not able to decompose organic substances into inorganic ones. Decomposers- microorganisms (bacteria and fungi) that destroy the dead remains of living beings, turning them into inorganic and simple organic compounds.
3. Name the organisms that should be in the missing place of the following food chains.
1) Spider, fox
2) caterpillar tree eater, snake hawk
3) caterpillar
4. From the proposed list of living organisms, make a food web:
grass, berry bush, fly, titmouse, frog, snake, hare, wolf, decay bacteria, mosquito, grasshopper. Indicate the amount of energy that passes from one level to another.
1. Grass (100%) - grasshopper (10%) - frog (1%) - already (0.1%) - decay bacteria (0.01%).
2. Shrub (100%) - hare (10%) - wolf (1%) - decay bacteria (0.1%).
3. Grass (100%) - fly (10%) - titmouse (1%) - wolf (0.1%) - decay bacteria (0.01%).
4. Grass (100%) - mosquito (10%) - frog (1%) - already (0.1%) - decay bacteria (0.01%).
5. Knowing the rule of energy transfer from one trophic level to another (about 10%), build a biomass pyramid of the third food chain (task 1). Plant biomass is 40 tons.
Grass (40 tons) - grasshopper (4 tons) - sparrow (0.4 tons) - fox (0.04).
6. Conclusion: what do the rules of ecological pyramids reflect?
The rule of ecological pyramids very conditionally conveys the pattern of energy transfer from one level of nutrition to the next, in the food chain. For the first time, these graphic models were developed by C. Elton in 1927. According to this pattern, the total mass of plants should be an order of magnitude greater than herbivores, and the total mass of herbivores by an order of magnitude. more predators first level, etc. to the very end of the food chain.
Lab #1
Introduction
1. Food chains and trophic levels
2. Food webs
3. Food connections of fresh water
4. Food connections of the forest
5. Energy losses in power circuits
6. Ecological pyramids
6.1 Pyramids of numbers
6.2 Biomass pyramids
Conclusion
Bibliography
Introduction
Organisms in nature are connected by the commonality of energy and nutrients. The entire ecosystem can be likened to a single mechanism that consumes energy and nutrients to do work. Nutrients initially come from the abiotic component of the system, to which, in the end, they return either as waste products or after the death and destruction of organisms.
Within the ecosystem, organic substances containing energy are created by autotrophic organisms and serve as food (a source of matter and energy) for heterotrophs. A typical example: an animal eats plants. This animal, in turn, can be eaten by another animal, and in this way energy can be transferred through a number of organisms - each subsequent one feeds on the previous one, supplying it with raw materials and energy. Such a sequence is called a food chain, and each of its links is called a trophic level.
The purpose of the abstract is to characterize the nutritional relationships in nature.
1. Food chains and trophic levels
Biogeocenoses are very complex. They always have many parallel and intricately intertwined power circuits, and total number species are often measured in hundreds and even thousands. Almost always different types feed on several different objects and themselves serve as food for several members of the ecosystem. The result is a complex network of food connections.
Each link in the food chain is called a trophic level. The first trophic level is occupied by autotrophs, or the so-called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. There are usually four or five trophic levels and rarely more than six.
Primary producers are autotrophic organisms, mainly green plants. Some prokaryotes, namely blue-green algae and a few species of bacteria, also photosynthesize, but their contribution is relatively small. Photosynthetics convert solar energy (light energy) into chemical energy contained in the organic molecules that make up tissues. A small contribution to the production of organic matter is also made by chemosynthetic bacteria that extract energy from inorganic compounds.
In aquatic ecosystems, the main producers are algae - often small unicellular organisms, which make up the phytoplankton of the surface layers of oceans and lakes. On the land most primary production is supplied by more highly organized forms related to gymnosperms and angiosperms. They form forests and grasslands.
Primary consumers feed on primary producers, that is, they are herbivores. On land, many insects, reptiles, birds and mammals are typical herbivores. The most important groups of herbivorous mammals are rodents and ungulates. The latter include grazing animals such as horses, sheep, large cattle adapted to run on fingertips.
In aquatic ecosystems (freshwater and marine), herbivorous forms are usually represented by mollusks and small crustaceans. Most of these organisms - cladocerans and copepods, crab larvae, barnacles and bivalves (such as mussels and oysters) - feed by filtering the smallest primary producers from the water. Together with protozoa, many of them make up the bulk of the zooplankton that feed on phytoplankton. Life in the oceans and lakes is almost completely dependent on plankton, since almost all food chains begin with it.
Plant material (e.g. nectar) → fly → spider →
→ shrew → owl
Rose bush juice → aphids → ladybug→ spider → insectivorous bird → bird of prey
There are two main types of food chains, grazing and detrital. Above were examples of pasture chains in which the first trophic level is occupied by green plants, the second by pasture animals, and the third by predators. The bodies of dead plants and animals still contain energy and construction material”, as well as intravital secretions, such as urine and feces. These organic materials are decomposed by microorganisms, namely fungi and bacteria, living as saprophytes on organic residues. Such organisms are called decomposers. They secrete digestive enzymes dead bodies or waste products and absorb the products of their digestion. The rate of decomposition may vary. Organic matter from urine, feces, and animal carcasses is consumed in a few weeks, while fallen trees and branches can take many years to decompose. A very significant role in the decomposition of wood (and other plant residues) is played by fungi, which secrete the enzyme cellulose, which softens the wood, and this allows small animals to penetrate and absorb the softened material.
Pieces of partially decomposed material are called detritus, and many small animals (detritivores) feed on them, accelerating the decomposition process. Since both true decomposers (fungi and bacteria) and detritophages (animals) participate in this process, both are sometimes called decomposers, although in reality this term refers only to saprophytic organisms.
Detritophages can, in turn, feed on more large organisms, and then another type of food chain is created - a chain, a chain that starts with detritus:
Detritus → detritus feeder → predator
The detritophages of forest and coastal communities include earthworm, wood lice, carrion fly larva (forest), polychaete, crimson, sea cucumber (coastal zone).
Here are two typical detritus food chains in our forests:
Leaf litter → Earthworm → Blackbird → Sparrowhawk
Dead animal → Carrion fly larvae → common frog→ Common snake
Some typical detritivores are earthworms, woodlice, bipedals, and smaller ones (<0,5 мм) животные, такие, как клещи, ногохвостки, нематоды и черви-энхитреиды.
2. Food webs
In food chain diagrams, each organism is represented as feeding on other organisms of the same type. However, real food chains in an ecosystem are much more complex, as an animal can feed on different types of organisms from the same food chain or even from different food chains. This is especially true for predators of the upper trophic levels. Some animals feed on both other animals and plants; they are called omnivores (such, in particular, is man). In reality, food chains are intertwined in such a way that a food (trophic) web is formed. A food web diagram can show only a few of the many possible relationships, and it usually includes only one or two predators from each of the upper trophic levels. Such diagrams illustrate the nutritional relationships between organisms in an ecosystem and serve as a basis for the quantitative study of ecological pyramids and ecosystem productivity.
3. Food connections of fresh water
Fresh water food chains consist of several successive links. For example, plant residues and bacteria developing on them are fed by protozoa, which are eaten by small crustaceans. The crustaceans, in turn, serve as food for fish, and the latter can be eaten by predatory fish. Almost all species do not feed on one type of food, but use different food objects. Food chains are intricately intertwined. An important general conclusion follows from this: if any member of the biogeocenosis falls out, then the system is not disturbed, since other food sources are used. The greater the species diversity, the more stable the system.
The primary source of energy in aquatic biogeocenosis, as in most ecological systems, is sunlight, thanks to which plants synthesize organic matter. Obviously, the biomass of all animals existing in a reservoir completely depends on the biological productivity of plants.
Often the reason for the low productivity of natural water bodies is the lack of minerals (especially nitrogen and phosphorus) necessary for the growth of autotrophic plants, or the unfavorable acidity of the water. The introduction of mineral fertilizers, and in the case of an acidic environment, the liming of water bodies contribute to the reproduction of plant plankton, which feed on animals that serve as food for fish. In this way, the productivity of fishery ponds is increased.
4. Food connections of the forest
The richness and diversity of plants that produce a huge amount of organic matter that can be used as food cause the development of numerous consumers from the animal world in oak forests, from protozoa to higher vertebrates - birds and mammals.
Food chains in the forest are intertwined in a very complex food web, so the loss of any one animal species usually does not significantly disrupt the entire system. The value of different groups of animals in the biogeocenosis is not the same. The disappearance, for example, in most of our oak forests of all large herbivorous ungulates: bison, deer, roe deer, elk - would have little effect on the overall ecosystem, since their numbers, and therefore biomass, have never been large and have not played a significant role in the general circulation of substances. . But if herbivorous insects disappeared, the consequences would be very serious, since insects perform an important function of pollinators in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in food chains.
Of great importance in the life of the forest are the processes of decomposition and mineralization of the mass of dying leaves, wood, animal remains and their metabolic products. Of the total annual increase in the biomass of above-ground parts of plants, about 3-4 tons per 1 ha naturally die off and fall off, forming the so-called forest litter. A significant mass is also made up of dead underground parts of plants. With the litter, most of the minerals and nitrogen consumed by plants return to the soil.
Animal remains are very quickly destroyed by dead beetles, skin beetles, larvae of carrion flies and other insects, as well as putrefactive bacteria. It is more difficult to decompose cellulose and other durable substances that make up a significant part of plant litter. But they also serve as food for a number of organisms, such as fungi and bacteria, which have special enzymes that break down fiber and other substances into easily digestible sugars.
As soon as the plants die, their substance is completely used by the destroyers. A significant part of the biomass is made up of earthworms, which do a great job of decomposing and moving organic matter in the soil. The total number of insects, shell mites, worms and other invertebrates reaches many tens and even hundreds of millions per hectare. The role of bacteria and lower, saprophytic fungi is especially great in the decomposition of litter.
5. Energy losses in power circuits
All species that make up the food chain subsist on the organic matter created by green plants. At the same time, there is an important regularity associated with the efficiency of the use and conversion of energy in the process of nutrition. Its essence is as follows.
In total, only about 1% of the radiant energy of the Sun incident on a plant is converted into the potential energy of chemical bonds of synthesized organic substances and can be further used by heterotrophic organisms for nutrition. When an animal eats a plant, most of the energy contained in the food is spent on various life processes, turning into heat and dissipating. Only 5-20% of food energy passes into the newly built substance of the animal's body. If a predator eats a herbivore, then again most of the energy contained in the food is lost. Due to such large losses of useful energy, food chains cannot be very long: they usually consist of no more than 3-5 links (food levels).
The amount of plant matter that serves as the basis of the food chain is always several times greater than the total mass of herbivorous animals, and the mass of each of the subsequent links in the food chain also decreases. This very important pattern is called the rule of the ecological pyramid.
6. Ecological pyramids
6.1 Pyramids of numbers
To study the relationships between organisms in an ecosystem and to graphically represent these relationships, it is more convenient to use ecological pyramids rather than food web diagrams. In this case, the number of different organisms in a given territory is first calculated, grouping them according to trophic levels. After such calculations, it becomes obvious that the number of animals progressively decreases during the transition from the second trophic level to the next. The number of plants of the first trophic level also often exceeds the number of animals that make up the second level. This can be displayed as a pyramid of numbers.
For convenience, the number of organisms at a given trophic level can be represented as a rectangle, the length (or area) of which is proportional to the number of organisms living in a given area (or in a given volume, if it is an aquatic ecosystem). The figure shows a pyramid of numbers, reflecting the real situation in nature. Predators located at the highest trophic level are called terminal predators.
When sampling - in other words, at a given point in time - the so-called growing biomass, or standing crop, is always determined. It is important to understand that this value does not contain any information about the rate of biomass formation (productivity) or its consumption; Otherwise, errors may occur for two reasons:
1. If the rate of biomass consumption (loss due to eating) approximately corresponds to the rate of its formation, then the standing crop does not necessarily indicate productivity, i.e. about the amount of energy and matter passing from one trophic level to another in a given period of time, for example, in a year. For example, on a fertile, intensively used pasture, the yield of standing grasses may be lower and the productivity higher than on a less fertile, but little used for grazing.
2. Producers of small sizes, such as algae, are characterized by a high rate of renewal, i.e. high rate of growth and reproduction, balanced by intensive consumption of them for food by other organisms and natural death. Thus, although standing biomass may be small compared to large producers (eg trees), productivity may not be less as trees accumulate biomass over a long period of time. In other words, phytoplankton with the same productivity as a tree will have a much lower biomass, although it could support the same mass of animals. In general, populations of large and long-lived plants and animals have a slower rate of renewal than small and short-lived ones and accumulate matter and energy for a longer time. Zooplankton have a higher biomass than the phytoplankton they feed on. This is typical for plankton communities in lakes and seas at certain times of the year; phytoplankton biomass exceeds zooplankton biomass during the spring "bloom", but in other periods the reverse ratio is possible. Such apparent anomalies can be avoided by using pyramids of energy.
Conclusion
Completing the work on the abstract, we can draw the following conclusions. A functional system that includes a community of living beings and their habitat is called an ecological system (or ecosystem). In such a system, the bonds between its components arise primarily on a food basis. The food chain indicates the path of movement of organic substances, as well as the energy and inorganic nutrients contained in it.
In ecological systems, in the process of evolution, chains of interconnected species have developed, successively extracting materials and energy from the original food substance. Such a sequence is called a food chain, and each of its links is called a trophic level. The first trophic level is occupied by autotrophic organisms, or the so-called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. The last level is usually occupied by decomposers or detritophages.
Food relationships in the ecosystem are not straightforward, since the components of the ecosystem are in complex interactions with each other.
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