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FOOD CHAIN FACTS

Introduction

In an ecosystem, plants capture the sun's energy and use it to convert inorganic compounds into energy-rich organic compounds1. This process of using the sun's energy to convert minerals (such as magnesium or nitrogen) in the soil into green leaves, or carrots, or strawberries, is called photosynthesis.

Photosynthesis is only the beginning of a chain of energy conversions. There are many types of animals that will eat the products of the photosynthesis process. Examples are deer eating shrub leaves, rabbits eating carrots, or worms eating grass. When these animals eat these plant products, food energy and organic compounds are transferred from the plants to the animals. These animals are in turn eaten by other animals, again transferring energy and organic compounds from one animal to another. Examples would be lions eating deer, foxes eating rabbits, or birds eating worms.

This chain of energy transferring from one species to another can continue several more times, but it eventually ends. It ends with the dead animals that are broken down and used as food or nutrition by bacteria and fungi. As these organisms, referred to as decomposers, feed from the dead animals, they break down the complex organic compounds into simple nutrients. Decomposers play a very important role in this world because they take care of breaking down (cleaning) many dead material. There are more than 100,000 different types of decomposer organisms! These simpler nutrients are returned to the soil and can be used again by the plants. The energy transformation chain starts all over again.

Names and word definitions

Producers. Organisms, such as plants, that produce their own food are called autotrophs. The autotrophs, as mentioned before, convert inorganic compounds into organic compounds. They are called producers because all of the species of the ecosystem depend on them.

Consumers. All the organisms that can not make their own food (and need producers) are called heterotrophs. In an ecosystem heterotrophs are called consumers because they depend on others. They obtain food by eating other organisms. There are different levels of consumers. Those that feed directly from producers, i.e. organisms that eat plant or plant products are called primary consumers. In the figure above the grasshopper is a primary consumer.

Organisms that feed on primary consumers are called secondary consumers. Those who feed on secondary consumers are tertiary consumers. In the figure above the snake acts as a secondary consumer and the hawk as a tertiary consumer. Some organisms, like the squirrel are at different levels. When the squirrel eats acorns or fruits (which are plant product), it is a primary consumer; however, when it eats insects or nestling birds, is it is a tertiary consumer.

Consumers are also classified depending on what they eat.

Herbivores are those that eat only plants or plant products. Example are grasshoppers, mice, rabbits, deer, beavers, moose, cows, sheep, goats and groundhogs.

Carnivores, on the other hand, are those that eat only other animals. Examples of carnivores are foxes, frogs, snakes, hawks, and spiders.

Omnivores are the last type and eat both plants (acting a primary consumers) and meat (acting as secondary or tertiary consumers). Examples of omnivores are:

Bears --They eat insects, fish, moose, elk, deer, sheep as well as honey, grass, and sedges.
Turtles -- They eat snails, crayfish, crickets, earthworms, but also lettuce, small plants, and algae.
Monkeys -- They eat frogs and lizards as well as fruits, flowers, and leaves.
Squirrels -- They eat insects, moths, bird eggs and nestling birds and also seeds, fruits, acorns, and nuts.
Trophic level. The last word that is worth mentioning in this section is trophic level, which corresponds to the different levels or steps in the food chain. In other words, the producers, the consumers, and the decomposers are the main trophic levels.
Food Webs

In looking at the previous picture, the concept of food chain looks very simple, but in reality it is more complex. Think about it. How many different animals eat grass? And from the Facts about Red-tailed Hawks page, how many different foods does the hawk eat? One doesn't find simple independent food chains in an ecosystem, but many interdependent and complex food chains that look more like a web and are therefore called food webs

Oaks rate a position at or very near the top of the wildlife food chain (or bottom of the ecological pyramid). They are the "staff of life" for many wild life species. The greatest food value comes from the acorn, especially during the winter season when other foods are scarce.

Squirrels, which are omnivores, are neither at the bottom or the top of the food chain. Since the feed from producers as well as primary consumers

Hawks, which are mature birds of prey, are at the top of the their food chain and of the ecological pyramid

How Many Species?

People often ask
how many different species there are of certain animals.

The answer can only be approximate as new species are still being discovered but here are some numbers of known species:

Earthworms - 4,000
Leeches - 500
Flatworms - 25,000

Molluscs - 100,000 including:
Slugs and snails - 77,000
Squids and Octopuses - 650
Bivalves - 20,000

Echinoderms - 7000 including:
Starfish - 1,500
Sea Urchins - 950
Brittle stars - 2,000
Feather stars and sea lillies - 625
Sea cucumbers - 1,150

Insects over 1,000,000 including:
Butterflies - 20,000
Moths - 145,000
Flies - 90,000
Ants - 11,844
Bees and wasps - 120,000
Dragonflies - 5,000
Cockroaches - 4,300 (only three are native to britain - The Dusky, The Lesser and The Tawny)
Beetles - 370,000

Arachnids 82,000 including:
Spiders - 40,000 (600 British)
Scorpions - 1,200
Pseudoscorpions or false scorpions - 2000 (25 British)
Whip Scorpions - 100
Tail-less Whip Scorpions - 136
Sun Spiders or Wind scorpions 900
Ticks and Mites - 32,000
Harvestmen - 4,500 (23 British)


Millipedes - 8,000
Centipedes - 3,000

Woodlice - 3,500 (37 British)
Crabs - 5,700
Lobsters and Crayfish - 400
Shrimps and Prawns - 2,000
Barnacles - 1,000

Sharks - 370
Skates and Rays - 340
Bony Fish - 24,500

Frogs and Toads - 3,500
Newts, Salamanders and Mudpuppies - 360

Turtles and Tortoises - 240
Lizards - 3,750
Snakes - 2,700
Crocodiles - 14
Alligators and Caimans - 7
Gharial - 1

Birds - 9,700 Including:
Ostrich - 1
Emu - 1
Rheas - 2
Kiwis - 3
Penquins - 16
Gulls and Terns - 95
Auks - 22
Ducks, Geese and Swans - 150
Grebes - 20
Owls - 135
Pigeons and doves - 300
Parrots, Cockatoos and Lories - 330
True Woodpeckers - 200
Toucans - 38
Kingfishers - 86
Bee Eaters - 24
Hornbills - 45
Hummingbirds - 315
Starlings and Mynahs - 106
Crows - 120
Warblers - 339
Thrushes - 304
Finches - 155
Sparrows - 35
Nuthatches - 21
Treecreepers - 14
Tits - 62

Mammals - 4,260 Including:
Kangaroos and Wallabies - 56
Wombats - 3
Koala - 1
Rodents - 1600
Elephants - 2
Big Cats - 7
Small cats - 28
Dogs - 35
Bears - 7
Mongooses - 27
Pandas - 2
Racoons - 6
Skunks - 13
Otters - 12
Badgers - 8
Hyaenas - 4
Bats - 960
Shrews - 246
Armadillos - 20
Sloths - 5
Anteaters - 4
Aardvarks - 1
Rabbits and Hares - 44
Whales and Dolphins - 76
Seals - 19
Fur Seals and Sea Lions - 14
Walrus - 1
Manatees and Dugong - 4
Rhinos - 5
Tapirs - 4
Horses - 2
Wild Asses - 2
Zebras - 3
Camels and Llamas - 6
Wild Pigs - 9
Giraffe 1
Lemurs - 22
Gibbons - 9
Hippos - 2
Deer - 41
Great Apes - 4 (Human, Chimpanzee, Gorilla and Orang-utan).

Ecosystem/Food chain Facts

An ecosystem is a community of plants and animals and its environment.

Herbivores are animals that eat only plants.

Carnivores are animals that eat only meat.

Omnivores eat meat and plants.

Detritivores eat only dead, decomposing plant or animal matter, or droppings.



A Food chain is the transfer of energy from organism to organism.
They usually start with a green plant that gets its energy from the sun. Here is an example:

Grass - rabbit - fox.

The grass is a food producer because it produces food for animals.

The rabbit is a consumer because it consumes (eats) grass, it is also prey because it is eaten by the fox. Animals that are eaten by other animals are prey. Grass is not prey because it is not an animal.

The fox is a consumer because it eats the rabbit and a predator because it eats animals. Predators are animals that kill and eat other animals.


Here are some more food chains:

Leaf - caterpillar - bluetit - sparrowhawk.
Corn - mouse - owl.
Leaf - snail - song thrush.
Acorn - squirrel - fox.
Leaf - caterpillar - beetle - hedgehog - fox.
Blackberry - mouse - badger
Plankton - mussel - starfish - crab - otter
Grass - grasshopper - frog - heron

Food chains can become connected to form food webs. For example;
The fox could eat the hedgehog, the squirrel, the mouse, the song thrush, the snail and the beetle.
The song thrush could eat the caterpillar and the snail.
The mouse could eat the corn, the acorn, the snail, the beetle and the caterpillar.
The squirrel could eat the acorn, the corn, the caterpillar and the beetle.

Draw a picture to include all of the above animals and then draw lines between each animal and its food. You will then have a food web.


Life cycles:
Egg - larva - pupa - ladybird
Egg - larva - pupa - butterfly
Egg - larva - pupa - house fly
Egg - nymph - dragonfly
Egg - nymph - damselfly
Egg - nymph - mayfly
Frogspawn - tadpole - froglet - frog ...


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