2.1 Species and Populations

A group of organisms sharing common characteristics that interbreed and produce fertile offspring

An environment which a species lives. This consists of abiotic (non-living) and biotic (living) factors

Where, when and how an organism makes a living

NOTE: there are differences between what niche the species occupies (fundamental niche) and what it actually occupies (realised niche).

The full potential of what can be occupied

What the species actually occupies

Group of organisms of the same species living in the same area at the same time and are capable of interbreeding

Non-living factors that influence the organisms and ecosystems

Living components of an ecosystem that directly or indirectly affect another organism

Made up of organisms and the physical environment and the interactions between the living and non-living components between them.

sunlight, temperature, salinity, pH, pollutants

They determine ecosystems and their adaptations

organisms, their interactions or their work

INCLUDES: predation, herbivory, parasitism, mutualism, disease and competition

The maximum number of a species that can be sustainably supported by a given area

Factors that slow down growth of a population as it reaches its carrying capacity

The study of factors that cause changes to population sizes.

All interactions result in one species having an effect on the population dynamics and the carrying capacity of the environment.

A relationship where two organisms live together

A relationship between two species where one (the parasite) lives in or on the other (the host) gaining its food from it.

e.g. ticks, tape worms

1. Endoparasites: live inside the host

2. Ectoparasites: live on the surface of the host

Relation between two or more species where all benefit and none suffer

i.e. lichen

= fungus on top of lichen benefits by obtaining sugars from algae

= algae benefits from minerals and water fungus absorbs and passes onto algae

When one partner is helped and the other is not significantly harmed

i.e. fern growing halfway up a tree trunk

when resources are limited, populations compete in order to survive

intraspecific competition: Within species

interspecific competition: between different species

• no two species can occupy the same niche so the degree to which niches overlap determines the degree of interspecific competition

One species out-competes the other

When one animal, the predator, eats another animal, the prey

• includes plants eating plants

• can be beneficial since it strengthens the breeding pool by eliminating weaker organisms

Animals that feed on plants

(some plants have defence mechanisms against this)

Describe a generalised response of populations to a particular set of conditions

• start with exponential growth (no limiting factors affect the growth at first)

• above a certain population size, the growth rate slows down resulting in a population of a constant size

• Numbers stabilise at the carrying capacity

• Shows a boom and bust pattern

• rapid growth continues well past carrying capacity

• Then suddenly collapses (dieback)

• Does not show gradual slow down of population size

• Controlled by abiotic factors