science world 2 – chapter 2
living together
FOOD CHAINS & WEBS
Food chain – shows the flow of food and therefore energy (i.e.
who is eating whom). An example is:
Sun
Grass
Grasshopper
Kookaburra Bacteria.
Producers – are plants (e.g. grass). They make their own food
via a process called photosynthesis.
Consumers – are animals (e.g. grasshopper, kookaburra).
They are unable to make their own food so they
consume plants or other animals to obtain energy.
They can be described as first order consumers
(e.g. grasshopper), second order consumers (e.g.
kookaburra), etc.
Herbivore – an animal that only eats plants.
Carnivore – an animal that only eats other animals (i.e. meat).
Omnivore – an animal that eats both plants and animals.
Food web – is formed when a number of food chains join
together, as animals often eat many types of food.
WHEN LIVING THINGS DIE
At any stage of a food web an animal or plant may die – its
stored energy is lost to the consumers relying on it. However,
scavengers and decomposers rely on the energy from these
dead organisms for their own survival.
Scavengers (e.g. ants, maggots, crows) are consumers that feed
on the flesh and organs of dead animals, thereby taking up that
organisms’ stored energy.
Decomposers (e.g. bacteria, fungi) release enzymes to break
down the remains of the organism. They then absorb these
smaller molecules to obtain the chemical energy they require.
They also release nutrients back into the soil that can be used by
the producers for growth.
1
ORGANISMS IN ECOSYSTEMS
A habitat is the place where an organism lives. Every living
thing has particular requirements, and will only live in a place
where these can be provided. Some of the things a habitat may
need to provide for an animal or plant include:
*
*
*
*
*
a source of food and water (i.e. not too much competition
from other organisms).
shelter and living space.
mating partners for reproduction.
protection from predators.
suitable climate and weather conditions.
The complex system of feeding relationships and interactions
with the non-living parts of an organisms’ habitat is called an
ecosystem. There are many different types of ecosystems e.g.
polar ecosystems, rainforest ecosystems, desert ecosystems, etc.
POPULATIONS & COMMUNITIES
A group of living things of the same species living in the same
habitat is called a population. When two or more groups of
different organisms live together and interact with each other in
the same habitat, they are described as forming a community.
Each of the organisms in a community relies on other organisms
in that community for food and sometimes for protection.
Populations in an ecosystem are affected by many factors,
including:
*
*
*
*
*
*
*
the weather.
availability of water.
the intensity of light (for plants).
soil conditions (for plants).
the amount of food available.
the number of predators and competitors.
the presence of disease organisms.
2