Animal food chain. The nature of the age structure of a population depends on the type of survival curve characteristic of a given population. What are food chains?
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Every organism must receive energy to live. For example, plants consume energy from the sun, animals eat plants, and some animals eat other animals.
A food (trophic) chain is the sequence of who eats whom in a biological community () to obtain nutrients and energy that support life.
Autotrophs (producers)
Autotrophs- living organisms that make their own food, that is, their own organic compounds, from simple molecules such as carbon dioxide. There are two main types of autotrophs:
- Photoautotrophs (photosynthetic organisms), such as plants, process energy sunlight for getting organic compounds- sugars - from carbon dioxide in progress . Other examples of photoautotrophs are algae and cyanobacteria.
- Chemoautotrophs obtain organic substances due to chemical reactions in which they are involved inorganic compounds(hydrogen, hydrogen sulfide, ammonia, etc.). This process is called chemosynthesis.
Autotrophs are the basis of every ecosystem on the planet. They make up the majority of food chains and webs, and the energy obtained through photosynthesis or chemosynthesis supports all other organisms in ecological systems. When we're talking about about their role in food chains, autotrophs can be called producers or producers.
Heterotrophs (consumers)
Heterotrophs, also known as consumers, cannot use solar or chemical energy, to produce their own food from carbon dioxide. Instead, heterotrophs obtain energy by consuming other organisms or their byproducts. People, animals, fungi and many bacteria are heterotrophs. Their role in food chains is to consume other living organisms. There are many species of heterotrophs with different ecological roles, from insects and plants to predators and fungi.
Destructors (reducers)
Another consumer group should be mentioned, although it does not always appear in food chain diagrams. This group consists of decomposers, organisms that process dead organic matter and waste, turning them into inorganic compounds.
Decomposers are sometimes considered a separate trophic level. As a group, they feed on dead organisms coming from different trophic levels. (For example, they are able to process decaying plant matter, the body of a squirrel malnourished by predators, or the remains of a deceased eagle.) In a sense, the trophic level of decomposers runs parallel to the standard hierarchy of primary, secondary, and tertiary consumers. Fungi and bacteria are key decomposers in many ecosystems.
Decomposers, as part the food chain, play an important role in maintaining a healthy ecosystem, because thanks to them, they return nutrients and moisture, which are subsequently used by producers.
Levels of the food (trophic) chain
Diagram of the levels of the food (trophic) chain
A food chain is a linear sequence of organisms that transfer nutrients and energy from producers to top predators.
The trophic level of an organism is the position it occupies in the food chain.
First trophic level
The food chain starts with autotrophic organism or producer producing its own food from primary source energy, usually solar or hydrothermal energy from mid-ocean ridges. For example, photosynthetic plants, chemosynthetic plants, etc.
Second trophic level
Next come the organisms that feed on autotrophs. These organisms are called herbivores or primary consumers and consume green plants. Examples include insects, hares, sheep, caterpillars and even cows.
Third trophic level
The next link in the food chain are animals that eat herbivores - they are called secondary consumers or carnivorous (predatory) animals(for example, a snake that feeds on hares or rodents).
Fourth trophic level
In turn, these animals are eaten by larger predators - tertiary consumers(for example, an owl eats snakes).
Fifth trophic level
Tertiary consumers are eaten quaternary consumers(for example, a hawk eats owls).
Every food chain ends with an apex predator or superpredator - an animal without natural enemies(for example, crocodile, polar bear, shark, etc.). They are the "masters" of their ecosystems.
When any organism dies, it is eventually eaten by detritivores (such as hyenas, vultures, worms, crabs, etc.) and the rest is decomposed by decomposers (mainly bacteria and fungi), and energy exchange continues.
Arrows in a food chain show the flow of energy, from the sun or hydrothermal vents to top predators. As energy flows from body to body, it is lost at each link in the chain. The collection of many food chains is called food web.
The position of some organisms in the food chain may vary because their diet is different. For example, when a bear eats berries, it acts as a herbivore. When it eats a plant-eating rodent, it becomes a primary predator. When a bear eats salmon, it acts as a superpredator (this is due to the fact that salmon is the primary predator, since it feeds on herring, which eats zooplankton, which feeds on phytoplankton, which produces own energy thanks to sunlight). Think about how people's place in the food chain changes, even often within a single meal.
Types of food chains
In nature, as a rule, there are two types of food chains: pasture and detritus.
Grassland food chain
Grassland food chain diagram
This type of food chain begins with living green plants to feed the herbivores on which carnivores feed. Ecosystems with this type of chain are directly dependent on solar energy.
Thus, the grazing type of food chain depends on the autotrophic capture of energy and its movement along the links of the chain. Most ecosystems in nature follow this type of food chain.
Examples of grazing food chains:
- Grass → Grasshopper → Bird → Hawk;
- Plants → Hare → Fox → Lion.
Detrital food chain
Detrital food chain diagram
This type of food chain begins with decaying organic material - detritus - which is consumed by detritivores. Then, predators feed on detritivores. Thus, such food chains are less dependent on direct solar energy than grazing ones. The main thing for them is the influx of organic substances produced in another system.
For example, this type of food chain is found in decomposing litter.
Energy in the food chain
Energy is transferred between trophic levels when one organism feeds on and receives nutrients from another. However, this movement of energy is inefficient, and this inefficiency limits the length of food chains.
When energy enters a trophic level, some of it is stored as biomass, as part of the body of organisms. This energy is available for the next trophic level. Typically, only about 10% of the energy that is stored as biomass at one trophic level is stored as biomass at the next level.
This principle of partial energy transfer limits the length of food chains, which typically have 3-6 levels.
At each level, energy is lost in the form of heat, as well as in the form of waste and dead matter that decomposers use.
Why does so much energy leave the food web between one trophic level and the next? Here are some of the main reasons for inefficient energy transfer:
- At each trophic level, a significant portion of energy is dissipated as heat as organisms perform cellular respiration and move around in daily life.
- Some organic molecules that organisms feed on cannot be digested and are excreted as feces.
- Not all individual organisms in a trophic level will be eaten by organisms from the next level. Instead, they die without being eaten.
- Feces and uneaten dead organisms become food for decomposers, who metabolize them and convert them into their energy.
So, none of the energy actually disappears - it all ends up producing heat.
Food chain meaning
1. Food chain studies help understand feeding relationships and interactions between organisms in any ecosystem.
2. Thanks to them, it is possible to evaluate the mechanism of energy flow and the circulation of substances in the ecosystem, as well as understand the movement toxic substances in the ecosystem.
3. Studying the food chain provides insight into biomagnification issues.
In any food chain, energy is lost every time one organism is consumed by another. In this regard, there should be much more plants than herbivorous animals. There are more autotrophs than heterotrophs, and therefore most of them are herbivores rather than carnivores. Although there is intense competition between animals, they are all interconnected. When one species goes extinct, it can affect many other species and have unpredictable consequences.
1. Producers(producers) produce organic substances from inorganic ones. These are plants, as well as photo- and chemosynthetic bacteria.
2. Consumers(consumers) consume finished organic substances.
- 1st order consumers feed on producers (cow, carp, bee)
- 2nd order consumers feed on first order consumers (wolf, pike, wasp)
etc.
3. Decomposers(destroyers) destroy (mineralize) organic substances to inorganic ones - bacteria and fungi.
Example of a food chain: cabbage → cabbage white caterpillar → tit → hawk. The arrow in the food chain is directed from the one who is eaten towards the one who eats. The first link of the food chain is the producer, the last is the higher-order consumer or decomposer.
The food chain cannot contain more than 5-6 links, because when moving to each next link, 90% of the energy is lost ( 10% rule, rule of the ecological pyramid). For example, a cow ate 100 kg of grass, but gained weight only by 10 kg, because...
a) she did not digest part of the grass and threw it away with feces
b) some of the digested grass was oxidized to carbon dioxide and water to produce energy.
Each subsequent link in the food chain weighs less than the previous one, so the food chain can be represented as biomass pyramids(at the bottom there are producers, there are the most of them, at the very top there are consumers of the highest order, there are the fewest of them). In addition to the biomass pyramid, you can build a pyramid of energy, numbers, etc.
Establish a correspondence between the function performed by the organism in the biogeocenosis and the representatives of the kingdom performing this function: 1) plants, 2) bacteria, 3) animals. Write the numbers 1, 2 and 3 in in the right order.
A) the main producers of glucose in the biogeocenosis
B) primary consumers of solar energy
C) mineralize organic matter
D) are consumers of different orders
D) ensure the absorption of nitrogen by plants
E) transfer substances and energy in food chains
Answer
Answer
Choose three options. Algae in a reservoir ecosystem constitute the initial link in most food chains, since they
1) accumulate solar energy
2) absorb organic substances
3) capable of chemosynthesis
4) synthesize organic substances from inorganic ones
5) provide energy and organic matter to animals
6) grow throughout life
Answer
Choose the one that suits you best correct option. In the ecosystem of a coniferous forest, consumers of the 2nd order include
1) spruce
2) forest mice
3) taiga ticks
4) soil bacteria
Answer
Install correct sequence links in the food chain using all named objects
1) ciliate-slipper
2) Bacillus subtilis
3) seagull
4) fish
5) mollusk
6) silt
Answer
Establish the correct sequence of links in the food chain using all the named representatives
1) hedgehog
2) field slug
3) eagle
4) plant leaves
5) fox
Answer
Establish a correspondence between the characteristics of organisms and the functional group to which it belongs: 1) producers, 2) decomposers
A) absorb carbon dioxide from the environment
B) synthesize organic substances from inorganic ones
B) include plants, some bacteria
D) feed on ready-made organic substances
D) include saprotrophic bacteria and fungi
E) decompose organic substances into minerals
Answer
1. Choose three options. Producers include
1) mold fungus - mukor
2) reindeer
3) common juniper
4) wild strawberries
5) fieldfare
6) lily of the valley
Answer
2. Choose three correct answers out of six. Write down the numbers under which they are indicated. Producers include
1) pathogenic prokaryotes
2) brown algae
3) phytophages
4) cyanobacteria
5) green algae
6) symbiont mushrooms
Answer
3. Choose three correct answers out of six and write down the numbers under which they are indicated. Producers of biocenoses include
1) penicillium mushroom
2) lactic acid bacterium
3) silver birch
4) white planaria
5) camel thorn
6) sulfur bacteria
Answer
4. Choose three correct answers out of six and write down the numbers under which they are indicated. Producers include
1) freshwater hydra
2) cuckoo flax
3) cyanobacterium
4) champignon
5) ulotrix
6) planaria
Answer
FORMED 5. Choose three correct answers out of six and write down the numbers under which they are indicated. Producers include
A) yeast
Choose three correct answers out of six and write down the numbers under which they are indicated. In biogeocenosis, heterotrophs, unlike autotrophs,
1) are producers
2) provide a change in ecosystems
3) increase the supply of molecular oxygen in the atmosphere
4) extract organic substances from food
5) convert organic residues into mineral compounds
6) act as consumers or decomposers
Answer
1. Establish a correspondence between the characteristics of an organism and its membership in the functional group: 1) producer, 2) consumers. Write numbers 1 and 2 in the correct order.
A) synthesize organic substances from inorganic ones
B) use ready-made organic substances
B) use inorganic substances soil
D) herbivores and carnivores
D) accumulate solar energy
E) use animal and plant foods as a source of energy
Answer
2. Match environmental groups in the ecosystem and their characteristics: 1) producers, 2) consumers. Write numbers 1 and 2 in the order corresponding to the letters.
A) are autotrophs
B) heterotrophic organisms
C) the main representatives are green plants
D) produce secondary products
D) synthesize organic compounds from inorganic substances
Answer
Answer
Establish the sequence of the main stages of the cycle of substances in the ecosystem, starting with photosynthesis. Write down the corresponding sequence of numbers.
1) destruction and mineralization of organic residues
2) primary synthesis of organic substances from inorganic substances by autotrophs
3) use of organic substances by consumers of the second order
4) energy use chemical bonds herbivores
5) use of organic substances by consumers of the third order
Answer
Establish the sequence of arrangement of organisms in the food chain. Write down the corresponding sequence of numbers.
1) frog
2) already
3) butterfly
4) meadow plants
Answer
1. Establish a correspondence between organisms and their function in the forest ecosystem: 1) producers, 2) consumers, 3) decomposers. Write the numbers 1, 2 and 3 in the correct order.
A) horsetails and ferns
B) molds
C) tinder fungi that live on living trees
D) birds
D) birch and spruce
E) putrefaction bacteria
Answer
2. Establish a correspondence between organisms - inhabitants of the ecosystem and the functional group to which they belong: 1) producers, 2) consumers, 3) decomposers.
A) mosses, ferns
B) toothless and pearl barley
B) spruce, larches
D) molds
D) putrefactive bacteria
E) amoebas and ciliates
Answer
3. Establish a correspondence between organisms and functional groups in the ecosystems to which they belong: 1) producers, 2) consumers, 3) decomposers. Write numbers 1-3 in the order corresponding to the letters.
A) spirogyra
B) sulfur bacteria
B) mukor
D) freshwater hydra
D) kelp
E) putrefaction bacteria
Answer
4. Establish a correspondence between organisms and functional groups in the ecosystems to which they belong: 1) producers, 2) consumers. Write numbers 1 and 2 in the order corresponding to the letters.
A) naked slug
B) common mole
B) gray toad
D) black polecat
D) kale
E) common cress
Answer
5. Establish a correspondence between organisms and functional groups: 1) producers, 2) consumers. Write numbers 1 and 2 in the order corresponding to the letters.
A) sulfur bacteria
B) field mouse
B) meadow bluegrass
D) honey bee
D) creeping wheatgrass
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated in the table. Which of the following organisms are consumers of ready-made organic matter in the pine forest community?
1) soil green algae
2) common viper
3) sphagnum moss
4) pine undergrowth
5) black grouse
6) wood mouse
Answer
1. Establish a correspondence between an organism and its membership in a certain functional group: 1) producers, 2) decomposers. Write numbers 1 and 2 in the correct order.
A) red clover
B) chlamydomonas
B) putrefaction bacterium
D) birch
D) kelp
E) soil bacterium
Answer
2. Establish a correspondence between the organism and the trophic level at which it is located in the ecosystem: 1) Producer, 2) Reducer. Write numbers 1 and 2 in the correct order.
A) Sphagnum
B) Aspergillus
B) Laminaria
D) Pine
D) Penicill
E) Putrefactive bacteria
Answer
3. Establish a correspondence between organisms and their functional groups in the ecosystem: 1) producers, 2) decomposers. Write numbers 1 and 2 in the order corresponding to the letters.
A) sulfur bacteria
B) cyanobacterium
B) fermentation bacterium
D) soil bacterium
D) mukor
E) kelp
Answer
Choose three options. What is the role of bacteria and fungi in the ecosystem?
1) convert organic substances of organisms into minerals
2) ensure the closure of the circulation of substances and energy conversion
3) form primary production in the ecosystem
4) serve as the first link in the food chain
5) form inorganic substances available to plants
6) are consumers of the second order
Answer
1. Establish a correspondence between a group of plants or animals and its role in the pond ecosystem: 1) producers, 2) consumers. Write numbers 1 and 2 in the correct order.
A) coastal vegetation
B) fish
B) amphibian larvae
D) phytoplankton
D) bottom plants
E) shellfish
Answer
2. Establish a correspondence between the inhabitants of the terrestrial ecosystem and the functional group to which they belong: 1) consumers, 2) producers. Write numbers 1 and 2 in the order corresponding to the letters.
A) alder
B) typograph beetle
B) elm
D) sorrel
D) crossbill
E) forty
Answer
3. Establish a correspondence between the organism and the functional group of the biocenosis to which it belongs: 1) producers, 2) consumers. Write numbers 1 and 2 in the order corresponding to the letters.
A) tinder fungus
B) creeping wheatgrass
B) sulfur bacteria
D) Vibrio cholerae
D) ciliate-slipper
E) malarial plasmodium
Answer
4. Establish a correspondence between the examples and ecological groups in the food chain: 1) producers, 2) consumers. Write numbers 1 and 2 in the order corresponding to the letters.
A) hare
B) wheat
B) earthworm
D) tit
D) kelp
E) small pond snail
Answer
Establish a correspondence between animals and their roles in the biogeocenosis of the taiga: 1) consumer of the 1st order, 2) consumer of the 2nd order. Write numbers 1 and 2 in the correct order.
A) nutcracker
B) goshawk
B) common fox
D) red deer
D) brown hare
E) common wolf
Answer
Answer
Determine the correct sequence of organisms in the food chain.
1) wheat grains
2) red fox
3) bug harmful turtle
4) steppe eagle
5) common quail
Answer
Establish a correspondence between the characteristics of organisms and the functional group to which they belong: 1) Producers, 2) Decomposers. Write numbers 1 and 2 in the correct order.
A) Is the first link in the food chain
B) Synthesize organic substances from inorganic ones
B) Use the energy of sunlight
D) They feed on ready-made organic substances
D) Return minerals into ecosystems
E) Decompose organic substances into minerals
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. In the biological cycle occurs:
1) decomposition of producers by consumers
2) synthesis of organic substances from inorganic by producers
3) decomposition of consumers by decomposers
4) consumption of finished organic substances by producers
5) nutrition of producers by consumers
6) consumption of finished organic substances by consumers
Answer
1. Select organisms that are decomposers. Three correct answers out of six and write down the numbers under which they are indicated.
1) penicillium
2) ergot
3) putrefactive bacteria
4) mukor
5) nodule bacteria
6) sulfur bacteria
Answer
2. Choose three correct answers out of six and write down the numbers under which they are indicated. Decomposers in an ecosystem include
1) rotting bacteria
2) mushrooms
3) nodule bacteria
4) freshwater crustaceans
5) saprophytic bacteria
6) chafers
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. Which of the following organisms are involved in the decomposition of organic residues to mineral ones?
1) saprotrophic bacteria
2) mole
3) penicillium
4) chlamydomonas
5) white hare
6) mukor
Answer
Establish the order of organisms in the food chain, starting with the organism that absorbs sunlight. Write down the corresponding sequence of numbers.
1) gypsy moth caterpillar
2) linden
3) common starling
4) sparrowhawk
5) fragrant beetle
Answer
Choose one, the most correct option. What do fungi and bacteria have in common?
1) the presence of cytoplasm with organelles and a nucleus with chromosomes
2) asexual reproduction using spores
3) their destruction of organic substances to inorganic ones
4) existence in the form of unicellular and multicellular organisms
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. In a mixed forest ecosystem, the first trophic level is occupied by
1) granivorous mammals
2) warty birch
3) black grouse
4) gray alder
5) angustifolia fireweed
6) dragonfly rocker
Answer
1. Choose three correct answers out of six and write down the numbers under which they are indicated. The second trophic level in a mixed forest ecosystem is occupied by
1) moose and roe deer
2) hares and mice
3) bullfinches and crossbills
4) nuthatches and tits
5) foxes and wolves
6) hedgehogs and moles
Answer
2. Choose three correct answers out of six and write down the numbers under which they are indicated. The second trophic level of the ecosystem includes
1) Russian muskrat
2) black grouse
3) cuckoo flax
4) reindeer
5) European marten
6) field mouse
Answer
Establish the sequence of organisms in the food chain. Write down the corresponding sequence of numbers.
1) fish fry
2) algae
3) perch
4) daphnia
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. In food chains, first-order consumers are
1) echidna
2) locusts
3) dragonfly
4) fox
5) moose
6) sloth
Answer
Place the organisms in the detrital food chain in the correct order. Write down the corresponding sequence of numbers.
1) mouse
2) honey fungus
3) hawk
4) rotten stump
5) snake
Answer
Establish a correspondence between the animal and its role in the savanna: 1) consumer of the first order, 2) consumer of the second order. Write numbers 1 and 2 in the order corresponding to the letters.
A) antelope
B) lion
B) cheetah
D) rhinoceros
D) ostrich
E) neck
Answer
Analyze the table “Trophic levels in the food chain.” For each lettered cell, select the corresponding term from the list provided. Write down the selected numbers in the order corresponding to the letters.
1) secondary predators
2) first level
3) saprotrophic bacteria
4) decomposers
5) second-order consumers
6) second level
7) producers
8) tertiary predators
Answer
Place the organisms in the correct order in the decomposition chain (detritus). Write down the corresponding sequence of numbers.
1) small carnivorous predators
2) animal remains
3) insectivores
4) saprophagous beetles
Answer
Analyze the table “Trophic levels in the food chain.” Fill in the blank cells of the table using the terms in the list. For each lettered cell, select the corresponding term from the list provided. Write down the selected numbers in the order corresponding to the letters.
List of terms:
1) primary predators
2) first level
3) saprotrophic bacteria
4) decomposers
5) consumers of the first order
6) heterotrophs
7) third level
8) secondary predators
Answer
Analyze the table “Functional groups of organisms in an ecosystem.” For each lettered cell, select the corresponding term from the list provided. Write down the selected numbers in the order corresponding to the letters.
1) viruses
2) eukaryotes
3) saprotrophic bacteria
4) producers
5) algae
6) heterotrophs
7) bacteria
8) mixotrophs
Answer
Look at the picture of a food chain and indicate (A) the type of food chain, (B) the producer, and (C) the second-order consumer. For each lettered cell, select the corresponding term from the list provided. Write down the selected numbers in the order corresponding to the letters.
1) detrital
2) Canadian pondweed
3) osprey
4) pasture
5) big pond snail
6) green frog
Answer
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. Decomposers in the forest ecosystem participate in the cycle of substances and energy transformations, since
1) synthesize organic substances from minerals
2) release energy contained in organic residues
3) accumulate solar energy
4) decompose organic matter
5) promote the formation of humus
6) enter into symbiosis with consumers
Answer
Establish the order in which the listed objects should be located in the food chain.
1) cross spider
2) weasel
3) dung fly larva
4) frog
5) manure
Answer
Choose two correct answers out of five and write down the numbers under which they are indicated. Environmental terms include
1) heterosis
2) population
3) outbreeding
4) consumer
5) divergence
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. Which of the following animals can be classified as consumers of the second order?
1) gray rat
2) Colorado beetle
3) dysenteric amoeba
4) grape snail
5) ladybug
6) honey bee
Answer
© D.V. Pozdnyakov, 2009-2019
Introduction
1. Food chains and trophic levels
2. Food webs
3. Freshwater food connections
4. Forest food connections
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 a 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 originate from the abiotic component of the system, to which they are ultimately returned either as waste products or after the death and destruction of organisms.
Within an ecosystem, energy-containing organic substances 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. This sequence is called a food chain, and each link is called a trophic level.
The purpose of the essay is to characterize food connections in nature.
1. Food chains and trophic levels
Biogeocenoses are very complex. They always have many parallel and complexly intertwined power circuits, and total number species are often measured in hundreds and even thousands. Almost always different types They 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.
The primary producers are autotrophic organisms, mostly 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 from which tissues are built. Chemosynthetic bacteria, which extract energy from inorganic compounds, also make a small contribution to the production of organic matter.
In aquatic ecosystems, the main producers are algae - often small single-celled organisms that make up the phytoplankton of the surface layers of oceans and lakes. On land, most of the primary production is supplied by more highly organized forms related to gymnosperms and angiosperms. They form forests and meadows.
Primary consumers feed on primary producers, i.e. they are herbivores. On land, typical herbivores include many insects, reptiles, birds and mammals. The most important groups of herbivorous mammals are rodents and ungulates. The latter include grazing animals such as horses, sheep, and cattle, which are adapted to running on their toes.
In aquatic ecosystems (freshwater and marine), herbivorous forms are usually represented by mollusks and small crustaceans. Most of these organisms—cladocerans, copepods, crab larvae, barnacles, and bivalves (such as mussels and oysters)—feed by filtering tiny primary producers from the water. Together with protozoa, many of them form the bulk of the zooplankton that feed on phytoplankton. Life in oceans and lakes depends almost entirely on plankton, since almost all food chains begin with them.
Plant material (e.g. nectar) → fly → spider →
→ shrew → owl
Juice rose bush→ aphid → 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 excretions, such as urine and feces. These organic materials decomposed by microorganisms, namely fungi and bacteria, living as saprophytes on organic residues. Such organisms are called decomposers. They release digestive enzymes onto 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 within weeks, while fallen trees and branches can take many years to decompose. Very significant role Fungi play a role in the decomposition of wood (and other plant debris), releasing 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, speeding up the decomposition process. Since both true decomposers (fungi and bacteria) and detritivores (animals) are involved in this process, both are sometimes called decomposers, although in reality this term refers only to saprophytic organisms.
Larger organisms can, in turn, feed on detritivores, and then a different type of food chain is created - a chain, a chain starting with detritus:
Detritus → detritivore → predator
Detritivores of forest and coastal communities include earthworm, woodlice, carrion fly larva (forest), polychaete, scarlet fly, holothurian (coastal zone).
Here are two typical detrital food chains in our forests:
Leaf litter → Earthworm → Blackbird → Sparrowhawk
Dead animal → Carrion fly larvae → Grass frog → Common grass snake
Some typical detritivores are earthworms, woodlice, bipeds 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 one type. However, actual food relationships in an ecosystem are much more complex because an animal may 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 eat both other animals and plants; they are called omnivores (this is the case, in particular, with humans). In reality, food chains are intertwined in such a way that a food (trophic) web is formed. A food web diagram can only show a few of the many possible connections, and it usually includes only one or two predators from each of the upper trophic levels. Such diagrams illustrate food relationships between organisms in an ecosystem and provide a basis for quantitative study ecological pyramids and ecosystem productivity.
3. Freshwater food connections
The food chains of a fresh water body consist of several successive links. For example, protozoa, which are eaten by small crustaceans, feed on plant debris and the bacteria that develop on them. 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 disrupted, 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.
Food or trophic chain call the relationship between different groups of organisms (plants, fungi, animals and microbes), in which energy is transported as a result of the consumption of 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 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 (approximately 85%) is lost when transferred from one link to another, it is dissipated, that 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 herbivores (first-order consumers), which are then eaten by carnivorous animals (second-order consumers). This 3-link food chain is an example of a proper food chain.
There are:
Pasture chains
Trophic chains begin with auto- or chemotrophs (producers) and include heterotrophs in the form of consumers of various orders. Such food chains are 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 food chain of a grassland (this could be a forest zone or a desert, in this case the only difference will be biological species various participants in the food chain and the ramifications 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 the butterfly - the third link in the chain, a consumer of the second order. The frog is swallowed by a snake - the fourth link and a consumer of the third order, the snake is eaten by a hawk - a consumer of the fourth order and the fifth, as a rule, the last link in the 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 sunlight can penetrate through the water column. This is a depth of 150-200 meters. Heterotrophs can also live in deeper layers, rising to the surface at night to feed with algae, and in the morning again going to the usual depth, making vertical migrations of up to 1 kilometer per day. In turn, heterotrophs, which are consumers of subsequent orders and live even deeper, rise in the morning to the level of habitat of consumers of the first order in order to feed on them.
Thus, we see that in deep bodies of water, usually seas and oceans, there is such a thing as a “food ladder.” Its meaning is that the organic substances that are created by algae in surface layers land are transported along the food chain to the very bottom. Taking this fact into account, the opinion of some ecologists that the entire reservoir can be considered a single biogeocenosis can be considered justified.
Detrital trophic relationships
To understand what the detrital food chain is, you need to start with the very concept of “detritus.” Detritus is a collection of remains of dead plants, corpses and end products of animal metabolism.
Detrital chains are typical for communities of inland waters, deep lake bottoms, and oceans, many of whose representatives feed on detritus formed by the remains of dead organisms from upper layers or accidentally entering a body of water from ecological systems located on land, in the form of, for example, leaf litter.
Bottom ecological systems of oceans and seas, where there are no producers due to the lack of sunlight, can exist only due to detritus, the total mass of which in the World Ocean in a calendar year can reach hundreds of millions of tons.
Detritus chains are also common in forests, where a considerable part of the annual increase in biomass of producers cannot be consumed directly by the first link of consumers. Therefore, it dies, forming litter, which, in turn, is decomposed by saprotrophs and then mineralized by decomposers. Important role in detritus formation forest communities mushrooms are playing.
Heterotrophs that feed directly on detritus are detritivores. In terrestrial ecological systems, detritivores include some species of arthropods, in particular insects, as well as annelids. Large detritivores among birds (vultures, crows) and mammals (hyenas) are usually called scavengers.
In ecological systems of waters, the bulk of detritivores are aquatic insects and their larvae, as well as some representatives of crustaceans. Detritivores can serve as food for larger heterotrophs, which, in turn, can also later become food for consumers of higher orders.
The links in the food chain are otherwise called trophic levels. By definition, this is a group of organisms that occupies a specific place in the food chain and provides a source of energy for each of the subsequent levels - food.
Organisms I trophic level in pasture food chains there are primary producers, autotrophs, that is, plants, and chemotrophs, bacteria that use energy chemical reactions for the synthesis of organic substances. In detrital systems, there are no autotrophs, and the first trophic level of the detrital trophic chain forms detritus itself.
Last, V trophic level represented by organisms that consume dead organic matter and final decay products. These organisms are called destructors or decomposers. Decomposers are mainly represented by invertebrate animals, which are necro-, sapro- and coprophages, using residues, waste and dead organic matter for food. Also included in this group are saprophagous plants that decompose leaf litter.
Also included in the level of destructors are heterotrophic microorganisms that are capable of converting organic substances into inorganic (mineral) substances, forming final products - carbon dioxide and water, which return to the ecological system and re-enter the natural cycle of substances.
The importance of food relationships
The main condition for the existence of an ecosystem is the maintenance of the circulation of substances and the transformation of energy. It is provided thanks to trophic (food) connections between species belonging to different functional groups. It is on the basis of these connections that organic substances, synthesized by producers from mineral substances with the absorption of solar energy, are transferred to consumers and undergo chemical transformations. As a result of the life activity of predominantly decomposers, the atoms of the main biogenic chemical elements pass from organic substances to inorganic ones (CO 2, NH 3, H 2 S, H 2 O). Inorganic substances are then used by producers to create new organic substances from them. And they are again drawn into the cycle with the help of producers. If these substances were not reused, life on Earth would be impossible. After all, the reserves of substances absorbed by producers in nature are not unlimited. To carry out a full cycle of substances in the ecosystem, all three must be present. functional groups organisms. And between them there must be constant interaction in the form of trophic connections with the formation of trophic (food) chains, or food chains.
A food chain (food chain) is a sequence of organisms in which a gradual transfer of matter and energy occurs from the source (previous link) to the consumer (subsequent link).
In this case, one organism can eat another, feeding on its dead remains or waste products. Depending on the type of initial source of matter and energy, food chains are divided into two types: pasture (grazing chains) and detrital (decomposition chains).
Grazing chains (grazing chains)- food chains that begin with producers and include consumers of different orders. IN general view The pasture chain can be shown with the following diagram:
Producers -> First order consumers -> Second order consumers -> Third order consumers
For example: 1) food chain of a meadow: red clover - butterfly - frog - snake; 2) food chain of the reservoir: chlamydomonas - daphnia - gudgeon - pike perch. The arrows in the diagram show the direction of transfer of matter and energy in the power circuit.
Each organism in the food chain belongs to a specific trophic level.
Trophic level is a set of organisms that, depending on their method of nutrition and type of food, constitute a certain link in the food chain.
Trophic levels are usually numbered. The first trophic level consists of autotrophic organisms - plants (producers), the second trophic level contains herbivorous animals (consumers of the first order), and the third and subsequent levels contain carnivores (consumers of the second, third, etc. orders).
In nature, almost all organisms feed not on one, but on several types of food. Therefore, any organism can be at different trophic levels in the same food chain depending on the nature of the food. For example, a hawk, eating mice, occupies the third trophic level, and eating snakes, the fourth. In addition, the same organism can be a link in different food chains, connecting them with each other. Thus, a hawk can eat a lizard, a hare or a snake, which are part of different food chains.
In nature, pasture chains in pure form do not meet. They are interconnected by common nutritional links and form food web, or power network. Its presence in the ecosystem contributes to the survival of organisms when there is a lack of a certain type of food due to the ability to use other food. And the wider the species diversity of individuals in an ecosystem, the more food chains there are in the food web and the more stable the ecosystem. The loss of one link from the food chain will not disrupt the entire ecosystem, since food sources from other food chains can be used.
Detrital chains (decomposition chains)- food chains that begin with detritus, include detritivores and decomposers, and end with minerals. In detrital chains, the matter and energy of detritus are transferred between detritivores and decomposers through the products of their vital activity.
For example: dead bird - fly larvae - molds - bacteria - minerals. If detritus does not require mechanical destruction, then it immediately turns into humus with subsequent mineralization.
Thanks to detrital chains, the cycle of substances in nature is closed. Dead organic substances in detrital chains are converted into minerals, which enter the environment and are absorbed from it by plants (producers).
Pasture chains are predominantly located in the above-ground, and decomposition chains - in the underground layers of ecosystems. The relationship between pasture chains and detrital chains occurs through detritus entering the soil. Detrital chains are connected with pasture chains through mineral substances extracted from the soil by producers. Thanks to the interconnection of pasture and detritus chains, a complex food network is formed in the ecosystem, ensuring the constancy of the processes of transformation of matter and energy.
Ecological pyramids
The process of transformation of matter and energy in pasture chains has certain patterns. At each trophic level of the pasture chain, not all of the consumed biomass is used to form the biomass of consumers at that level. A significant part of it is spent on the vital processes of organisms: movement, reproduction, maintaining body temperature, etc. In addition, part of the feed is not digested and ends up in the body in the form of waste products. environment. In other words, most of the matter and the energy it contains is lost during the transition from one trophic level to another. The percentage of digestibility varies greatly and depends on the composition of the food and biological features organisms. Numerous studies have shown that at each trophic level of the food chain, on average, about 90% of energy is lost, and only 10% passes to the next level. American ecologist R. Lindeman in 1942 formulated this pattern as 10% rule. Using this rule, it is possible to calculate the amount of energy at any trophic level of the food chain, if its indicator is known at one of them. With some degree of assumption, this rule is also used to determine the transition of biomass between trophic levels.
If at each trophic level of a food chain we determine the number of individuals, or their biomass, or the amount of energy contained in it, then a decrease in these quantities will become obvious as we move towards the end of the food chain. This pattern was first established by the English ecologist C. Elton in 1927. He called it rule of the ecological pyramid and suggested expressing it graphically. If any of the above characteristics of trophic levels are depicted in the form of rectangles with the same scale and placed on top of each other, then the result will be ecological pyramid.
There are three types of ecological pyramids. Pyramid of numbers reflects the number of individuals in each link of the food chain. However, in the ecosystem the second trophic level ( consumers of the first order) may be numerically richer than the first trophic level ( producers). In this case, the result is an inverted pyramid of numbers. This is explained by the participation in such pyramids of individuals that are not equal in size. An example would be a pyramid of numbers consisting of deciduous tree, leaf-eating insects, small insectivores and large birds of prey. Biomass pyramid reflects the amount of organic matter accumulated at each trophic level of the food chain. The pyramid of biomass in terrestrial ecosystems is correct. And in the pyramid of biomass for aquatic ecosystems, the biomass of the second trophic level, as a rule, is greater than the biomass of the first when it is determined at a particular moment. But since aquatic producers (phytoplankton) have high speed formation of products, then ultimately their biomass during the season will still be greater than the biomass of consumers of the first order. This means that in aquatic ecosystems the rule of the ecological pyramid is also observed. Pyramid of Energy reflects patterns of energy expenditure at different trophic levels.
Thus, the supply of matter and energy accumulated by plants in pasture food chains is quickly consumed (eaten away), so these chains cannot be long. They usually include three to five trophic levels.
In an ecosystem, producers, consumers and decomposers are connected by trophic links and form food chains: grazing and detritus. In grazing chains, the 10% rule and the ecological pyramid rule apply. Three types of ecological pyramids can be built: numbers, biomass and energy.