Page 19 - prim 5 booklet 2025 modified

Delta Modern Language Schools

Science department

Grade 5

1st term 2024 -2025 E

Energy in the overall system remains the same:

• 10% only transfer between living organisms.

• 90% of this energy returns back to soil by decomposers.

Pollution
➢ When an ecosystem changes, food webs change too.
➢ Pollution affects the food resources and habitats of living organisms and this may lead to

the death of these organisms.

➢ Relationships between organisms have important role in keeping ecosystem balanced.

• Factors affecting the ecosystem:-

1. Increasing or decreasing the amount of water.
2. Increasing or decreasing the temperature.
3. Climate change. ( if the climate is suitable the population increases, but if it is unsuitable

the population of species decreases).

Population :

It is the number of organisms of one type of species living in an area.

➢ In an ecosystem, all species depend on each other for survival, so the decrease or increase
in one species affects the population of other species causing a population change.
Examples:-
➢ The population of microorganisms affects on the seabirds.

Micro organisms Small fish Sea bird
( consumer ) (consumer)
( Producer in marine
food web)

- Microorganisms can make their own food and found in cold water habitats.

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