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Organisms in their Environment
All living things need have requirements for survival. Animals need oxygen, food,
shelter, space, and water to survive. Plants need carbon dioxide, nutrients,
sunlight, and water to survive.
Animals also have physical characteristics which help them survive:
Camouflage to help them hide from predators
Webbed feet to help them swim fast to get food or to escape predators
Strong eyesight to see animals from far away (eagles)
Eyes on the side to see predators and hide
Eyes in front to hunt prey
Long legs to run fast
Fins and a sleek body to swim fast
A hard shell for protection from predators
Strong legs to run fast
Good sense of smell to locate food
Sharp teeth and claws for catching and eating animals
All living things fall into two categories, producers or consumers.
Producers are plants which make their own food and get their energy from
the sun.
Consumers need to eat food to get energy.
Consumers fall into 5 categories:
Herbivores: Eat only plants. Deer, cows, horses, grasshoppers, and
caterpillars are herbivores. Herbivores tend to have flat teeth for grinding
plants.
Carnivores: Eat only animals. Sharks, hawks, lions, panthers, and killer whales
are carnivores. Carnivores hunt, tend to be powerful, and have sharp teeth
or beaks and sharp claws for killing and eating other animals.
Omnivores: Eat both plants and animals. People, raccoons, birds, and bears
are omnivores.
Scavengers: Eat dead animals that they find lying around. Crows, vultures,
raccoons, rats, and seagulls are scavengers.
Decomposers: Are organisms that break down dead or decaying organisms.
Fungi, maggots, worms, and bacteria are decomposers.
Food chains show one path of energy (how energy passes from one living thing to
another). All food chains begin with a producer (a plant which gets its energy from
the sun). The plant passes its energy to the animal that eats it (a herbivore or
omnivore). This animal is eaten by another animal (an omnivore or carnivore) and it
receives the energy. Arrows point to the animal that is receiving the energy.
All animals depend on
plants for survival even
if they do not eat
plants. Carnivores eat
animals
which
eat
plants. If there weren’t
any plants for the
herbivores
to
eat,
there wouldn’t be any
herbivores
for
the
carnivores to eat.
Food webs are many food chains connected together.
Animals in a food chain are either predators (the hunters) or prey (the animal
hunted and eaten). Animals that are predators can become prey to larger animals.
Prey
Mouse
Snake
Caterpillar
Bird
Fish
Predator
is hunted and eaten by
is hunted and eaten by
is hunted and eaten by
is hunted and eaten by
is hunted and eaten by
Snake
Hawk
Bird
Cat
Bear
Many things can affect a food web.
If you remove an animal from a food chain it would affect the organisms
above and below it in the chain. First it would affect their food source or
prey. Their prey would increase in numbers because the lost animal would not
be there to eat it. Other animals which eat this prey would have more to eat
and may increase in number. The missing animal will affect their predators,
because they would have less food to help them survive. They would have to
rely on other sources of and their numbers might decrease.
If you remove part of the habitat (a tree, a field, part of a forest) the
animals that live there will need to find food and shelter elsewhere.
If the number of one organism changes, the balance of plants and animals in
a habitat is affected. Other populations will also change.
Lightneing starts a forest fire – destroys food webs.
Late Spring Frost - kills plants – animals suffer with less food
Red Oak trees disappear – Mice would feed on different plants. Some mice
would not survive. Hawks and snakes have less food.
Pesticides and Poisons – Kills plants – animals suffer
DDT (people) – Used to kill insects. Hawks and other birds became
contaminated. Eggshells weaken and break. Babies died.
People (New species of plant or animal introduced to an area) –
o Kudzu vine from Japan grows over many trees in Appalachian and
cause plants to die.
o Killer bees from Africa kill off native bees and take over. They have
no natural enemies here.
o Invasive species purple Loosestrife takes over cattail marsh areas.
Cattails are forced out. Animals which eat cattails starve.
o Rats escaped off ships from Europe to Hawaii. They have no
predators there and multiplied eating the eggs of the nene goose.
To protect the goose the people of Hawaii introduced the rateating mongoose from India to hunt the rats. Unfortunately the
mongoose preferred the nene goose eggs to the rats causing
them to be endangered.