Genetics, Populations, Evolution, and Ecosystems

What is a niche?

• What each species in an ecosystem occupies

• E.g. their role in the ecosystem or community, what it eats, and when it eats.

• Can be biotic or abiotic and can be separated by time, location or behaviour.

Biotic examples of niches

• What it eats and what organisms eat it.

Abiotic examples of niches

• The temperature range an organism can tolerate, the time of day that it is active e.g. nocturnal.

What happens if organisms occupy the same niches?

• they will compete as if they are the same species because they are sharing resources.

• If no interbreeding occurs then the species with the higher birth rate will outcompete the other species and take over the niche UNLESS one can adapt to change their niche e.g. eat a different food source.

Problems with investigating niches

• A proper ecosystem can never be replicated because the number of variables are too high.

• Taking away variables doesn’t mean that you are controlling them and if these are influential, then they might change you results.

• Competition may be forced in experiment e.g. in ecosystem there may be different food sources available.

Also competitive exclusion means they are competing and technically share same niche and resource partitioning means they have separate niches.

Animals become adapted to their niche

• An adaptation is a feature that members the same species have the increases their survival chances and reproduction in their habitation, increasing the frequency of advantageous alleles → natural selection over many generations → evolution.

• Every species has had to adapt to use the ecosystem in a way no other species can in order to occupy their own unique niche.

• Organisms are adapted to both the biotic e.g. specific predators (thorns) and abiotic e.g. temperature (thick fur).

What is a habitat?

The environment in which an organism lives in.

What is a population?

The total number of organisms of the same species living in the same geographical area.

What is a community?

The populations of all the different species that live in the same habitat.

What is an ecosystem?

Both the biotic and abiotic parts of an environment and how they interact.

What do plants compete with each other for?

• Light

• Space

• Water

• Mineral ions in the soil

What do animals compete with each other for?

• Food

• Water

• Mating partners

• Territory

What is interdependence?

Where, in a community, each species depends on other species for things such as food, shelter, pollination and seed dispersal.

What is a stable community?

A community where all the species and environmental factors are in balance, so that the population sizes are roughly constant.

What are the 4 different biotic factors that might affect organisms in an ecosystem?

• Availability of food

• Arrival of new predator

• Competition

• New pathogens

What are the 7 different abiotic factors?

• Light intensity

• Temperature

• Water/moisture levels

• pH and mineral content of the soil

• Wind intensity and direction

• Carbon dioxide levels (for plants)

• Oxygen levels (for aquatic animals)

Significance of availability of food

If the availability of food falls, then the number of organisms in that community will also fall

Significance of the arrival of a new predator

• Can cause the population of a prey species to fall

• Can also affect existing predators e.g. if they’re competing for the same prey

Significance of competition (between species)

If a species is outcompeted then it’s population can fall so much that numbers are no longer sufficient to breed and the species may become extinct.

Significance of new pathogens

If an infectious disease emerges and then spreads, it can wipe out a population of a species.

Significance of light intensity

• All plants need light to carry out photosynthesis; if the light intensity is too low then the rate of photosynthesis falls and the plants will grow more slowly.

• This is significance because if plants grow more slowly, then animals that eat plants may not have enough food

Significance of temperature

• If the temperature of an environment changes then this could cause the distribution of species to change

• E.g. animals could migrate and plant species might disappear from that area.

Significance of water/ moisture levels

It’s a significance abiotic factor as without water, both plants and animals can’t survive.

Significance of pH and mineral content of the soil

• Many plants cannot grown on soil which is too acidic or too alkaline

• Plants also require certain minerals in the soil e.g. nitrate which is used to make amino acids for proteins

Significance of wind intensity and direction

• Strong winds blowing inland from the sea can cause plants to lose water

Significance of carbon dioxide levels (for plants)

• Plants need carbon dioxide to photosynthesise and if carbon dioxide levels fall then the rate of photosynthesis can also decrease, meaning that the plant grows more slowly. If plants grow slower, then animals that feed on plants may not have enough food.

Significance of oxygen (for aquatic animals)

• Oxygen is needed for aerobic respiration

• The level of dissolved oxygen in water can decrease e.g. on hot days. This is harmful to aquatic organisms such as fish.