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34 Cards in this Set

  • Front
  • Back

define a habitat

A place where a community of organisms lives

Define ecosystem

Made up of all the interacting biotic (living) and abiotic (non living) features in a specific area

Define population

A group of interbreeding organisms of one species in a habitat

Define community

All the populations of different organisms living and interacting in a particular place at the same time

Define niche

An organisms role within the environment

Define ecology

The study of inter relationships between organisms and the environment

Define abiotic factors and give 3 examples

Non living


light intensity

oxygen availability

Altitude ( topography)


food availability

Define biotic factors and give 3 examples

Living factors






Define abundance

The total number of individuals of a species within a given area

Give two ways abundance can be measured

Percentage cover - how much of the quadrat is covered

Frequency - how many of the quadrats the species occurs in

Name two sampling techniques

Random sampling (frame quadrats) or systematic sampling (along transects)

Describe the method of random sampling

lay out two tapes at right angles in the area of study

obtain a series of coordinates using random numbers (from calculator or computer)

place quadrat at coordinates

record species within it

Describe the method of systematic sampling along a transect

Lie tape across ground in a straight line

any organism over which the line passes is recorded

What is a belt transect

Two parallel lines normally a metre wide

species within the lines are recorded

Equation for population size (mark release recapture)

Estimated population = total number of individuals in the first sample x total number of individuals in the second sample

\ number of marked individuals recaptured

Describe the techniques of mark release recapture

A known number of animals are caught

they are marked in some way

they are released back into the community

some time later

a given number of individual is collected randomly

number of marked individuals is recorded

Mark release recapture relies on assumptions name 3

Proportion of marked to unmarked is the same in sample as it is in the population as a whole

marked individuals in the first sample distribute themselves evenly

the population has a definite boundary ( no immigration or emigration)

there are few if any deaths and births

method of marking is not toxic or makes indivula more liable to predation

mark is not lost or rubbed off

Describe the Population growth curves

(3 main features)

1. Slow growth- small number of individuals slowly reproduce

2. Rapid growth - ever increasing number of individuals continue to reproduce (gradient of curve is steep)

3. Population growth declines until size remains more or less stable (due to food supply or increased predation)

What happens to population size over time And why

Decreases due to limiting factors which causes population to slow/cease

Define intraspecific competition

Competition between members of the same species

eg food water breeding sites

Define interspecific competition

Competition between members of different species

Define predation

Where one organism consumes another

What is the main problem with investigating predation in a lab

In a lab the prey rarely escape whereas in the wild prey can escape so the population will fall low but rarely become extinct

Describe the effect of predator- prey relationships on population size

(5 points)

Predators eat prey reduce population size

fewer prey predators are in greater competition

predator population is reduced

Fewer predator, fewer prey eaten

prey population increase

predator population increases

(more food available)

Apart from predator prey relationships wha can effect population size

Disease and climatic factors

Factors that effect human populations

food availability





birth rate

death rate

Define immigration

Where individuals join a population from the outside

Define emigration

Where individuals leave a population

Equation for population growth

(Births+ immigration) - (deaths + emigration)

Equation for population growth rate

Population change in period /. X100

population at start

Factors affecting birth rate (5 points)

Economic conditions - LEDC have higher birth rates

religion- some are opposed to birth control and some encourage larger families

social pressures - some cultures large families improves social standing

birth control - contraception and abortion

political factors - governments influence birth rates through education and taxation policies

Equation for birth rates

Total birth rates / total population x1000

Factors affecting death rates (7 points possible)

Age profile - more elderly means higher death rate

life expectancy at birth - economically developed countries live longer

Food supply

safe drinking water and sanitation

medical care

natural disasters


Equation for death rate

Number of deaths / total population x 1000