Keystone species

Food chains

a series of organisms each dependent on the next as a source of food.

Food webs

A food web consists of all the food chains in a single ecosystem. Each living thing in an ecosystem is part of multiple food chains. Each food chain is one possible path that energy and nutrients may take as they move through the ecosystem.

Keystone species

* When a keystones species is removed from the ecosystem, the ecosystem becomes much less stable and its structure changes.

The great white shark

* The great white shark is an Apex predator (top of the food chain)
* They keep populations of fish, seals and sea lions and smaller sharks in check.

The impact of a declining population

* The loss of an apex predator has lead to a drastic increase in the populations of mesopredators (mid-level predators)
* This increase then leads to a decrease in the populations of the prey of the now abundant mesopredators.

Keystone species and habitat

Some keystone species are needed to conserve habitats

Distribution of populations

* Distribution - the spread of members of a population over space (area)
* Populations may have identical densities but their distribution can differ.

Distribution

* Clumped and uniform distributions are both non-random patterns
* A uniform distribution may indicate a high level of intraspecific competition
* A random distribution is expected when the environmental conditions within the sample area are the same throughout the entire area and the presence of one member of a population has no effect on the location of another member of the population

Abundance and density

* Density - Number of individuals of a given species per unit area.
* Abundance - The total number of organisms of a given species

Why is measuring abundance important

**Conservation**

* Measuring the abundance of populations of endangered species over time to decide if the populations are stable, increasing of decreasing (Decreasing abundance leads to extinction)



**Control or elimination**

* Exotic pest species



**Measuring the diversity of a community**



**To understand why populations ‘explode’ or sharply increase in number**

Factors affecting population’s

* Chance environmental events
* Births
* Deaths
* Migration

Factors that affect population size and density

* Density - Independence factors
* Affect a population’s size regardless of the size density of the population
* Include conditions in which the species can survive and major changes or disturbances to the environment
* Density - Dependent factors
* Influence the rate of births and deaths in a population
* Include competition for resources, predation, crowding, paratism and infectious disease.

Indigenous Australian Connection to Land

* They have a deep interconnectedness with the land and believe that damage to the land is detrimental to the wellbeing of indigenous people.
* They have a strong belief in sustainable practices regarding human interaction with the environment.