Ecology

KEY WORDS

Habitat -The place where an organism lives.

Population - All the organisms of the same species living in one habitat.

Community - The population of different species living in a habitat.

Abiotic Factors - Non-living factors of the environment, e.g. temperature.

Biotic Factors - Living factors of the environment, e.g. food.

Ecosystem - The interaction of a community of biotic and abiotic parts of the environment.

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ORGANISMS COMPETE FOR RESOURCES TO SURVIVE

Organisms need things from the environment and other organisms to survive and reproduce:

  • Plants need light and its territory, as well as water and mineral ions from the soil.
  • Animals need their territory, food, water, and mates.

Organisms compete with other species (or the same species) for the same resources.

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ANY CHANGE IN ANY ENVIRONMENT CAN HAVE KNOCK-ON EF

In a community, each species depends on other species for food, shelter, pollination and seed dispersal - this is called interdependence.

A major change in the ecosystem (one species becomes extinct) can have far-reaching effects.

A stable community is one in which the size of the populations of all species remains relatively constant over time.

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ABIOTIC AND BIOTIC FACTORS

The environment in which organisms live changes all the time.

The things that change are either abiotic (non-living) or biotic (living) factors.

These can have an effect on a community...

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ABIOTIC FACTORS CAN VARY IN AN ECOSYSTEM

Abiotic factors are non-living factors. For example:

- Moisture level

- Light intensity

- Temperature

- CO2 level (for plants)

- Wind intensity and direction

- O2 level (for aquatic animals)

- Soil pH and mineral content 

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CHANGES IN ABIOTIC FACTORS CAN AFFECT POPULATIONS

A change in the environment could be an increase or decrease in an abiotic factor (an increase in temperature). These can affect the size of populations in a community.

This means they can also affect the population sizes of other organisms that depend on them.

FOR EXAMPLE:

  • A decrease in light intensity, temperature or level of CO2 could decrease the rate of photosynthesis in a plant species.
    • This could affect plant growth and cause a decrease in population size.
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BIOTIC FACTORS CAN VARY IN AN ECOSYSTEM

Biotic factors are living factors. For example:

- New predators arriving

- Competition (One species may outcompete another species)

- New pathogens

- Availability of food 

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CHANGES IN BIOTIC FACTORS CAN HAVE SERIOUS EFFECTS

A change in the environment could be an introduction of a new biotic factor, e.g. a new predator or pathogen.

These can affect the sizes of populations in a community which can have indirect effects because of interdependence.

For example:

  • A new predator could cause a decrease in the prey population.
    • Red and grey squirrels live in the same habitat and eat the same food.
    • Grey squirrels outcompete the red squirrels - the population of red squirrels is decreasing.
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