PortSaid international schools.
Science department
Food relationships among living organisms
1- Predation:
It is a food relationship among living organisms, where one living
organism devours another one.
Predation in animals.
(a lion prey a deer - a wolf preys a rabbit - a cat preys a rat)
Predation is a temporary relationship which ends by
devouring the prey or a part of it.
Predation is less common in the plant world than in animal
world.
Predation in plants.
Plants are autotrophic (self feeders) organisms.
plants make their own food by photosynthesis process. But some
plants cannot absorb some compounds from the soil to make
protein. these plants prey some tiny animals such as insects to
get their required elements for making protein. These plants are
known as insect-eaters or insectivorous plants
(drosera –dieonia)
Give reason :
Drosera is an insectivorous plant?
Because it preys some insects to get the required elements for
making protein.
Some ways of self-defence against predation in living organisms.
PortSaid international schools.
Science department
1- Camouflage:
A phenomenon in which a living organism can change
its color to simulate the color of its surrounding environment.
(fish, frogs, birds, chameleon, and most insects as butterflies.)
Cuttlefish(sepia) ejects a black color fluid in the surrounding water
when attacked by its enemies.
2- Mimicry:
A phenomenon in which the harmless living organisms imitate
other harmful or poisonous living organisms to fear their enemies
and escape from them.
(Some bees look like wasps in forming stripes on their bodies.)
2- Symbiosis:
a- Mutualism:
It is a food relationship between two different types of living
organisms in which, each organism gets benefit from the other.
Ex:•The relationship between nodular bacteria and leguminous
plants. The bacteria fix nitrogen in an organic form to provide the
plant with and plant provides bacteria with sugar made by plants
during photosynthesis process.
b- Commensalism:
It is a food relationship between two living organisms in which one
of them benefits from the other while the other neither benefit nor
harmed.
Examples:
Tiny aquatic organisms get shelter and food from canals and
fissures of a sponge while the sponge neither get benefit nor
harmed.
PortSaid international schools.
Science department
c- Parasitism:
It is a food relationship between two different kinds of
living organisms, one benefits from the other and is known as the
parasite, while the other is harmed and is known as the host.
Give reason:
The death of the host is considered a loss to the parasite?
Because the parasite will lose its source of food and shelter.
There are two types of parasitism:
a. External parasitism:
The parasite lives externally on the host's body and feeds by
sucking the blood of the host. The parasite conveys diseases to
the host.
Ex:Jawless lamprey sucks fish's blood.
Mosquitoes – lice – fleas – bugs - ticks
Mosquitoes cause malaria disease.
Fleas can convey small pox disease.
b. Internal parasitism:
The parasite lives internally inside the host's body and shares the
host its digested food or feeds on its tissues and cells.
Ex:
(Liver worms – Tape worms – Ascaris worms – Flaria worms –
Bilharzia worms)
Ascaris worms cause Anaemia.
Flaria worm causes Elephantiasis disease
Bilharzia worms cause Bilharziasis disease
PortSaid international schools.
Science department
3-Saprophytism:
It is a food relationship in which saprophytes
(decomposers) get their food by decomposing food remains or
bodies of dead organisms.
Give reason:
Bread mold fungus is saprophytic organism?
Because it gets its food by decomposing food remains (moist
bread).