Unit 4 Section 1

The place where an organism lives.

All the organisms of one species in a habitat.

populations of different species in a habitat make up a community.

all the organisms living in a particular area and all the non-living conditions

the non living features of an ecosystem.

eg temperature

the living features of the ecosystem.

eg predators

the role of a species within its habitat,

the abitoic and biotic interactions.

a feature that members of a species have that increases there chances of survival and reproduction.

the number of individuals of one species in a particular area.

esitmated by counting the number of individuals in samples taken.

or frequency can be used to measure abundance, - eg 70% of samples

or for plants, percentage cover.

where a particular species is in the area that you are investigating.

number caught in 1st sample X number caught in 2nd sample
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                     number marked in 2nd sample

!. Capture a sample of species.
2. Mark them in a harmelss way.
3. release them back into their habitat.
4. wait some time, then take a second sample from the same population.
6. count how many are marked.
7. use the equatuion to estimate population size.

1. The marked sample has had enough time and opportunity to mix back in with the popualtion.

2. the marking hasnt affected the indivuals chance of survival, and is still visible.

3. Changes in popualtion size due to births, deaths and migration are small during the period of study.

the total number of organisms of one species in a habitat.

when abiotic conditions are ideal for a species an organism can grow fast and reproduce successfully = increased pop. size

when abiotic condituions arent ideal for a species, organisms cant grow as fast or reproduce as successfully = decreased pop. size

Interspecific competition

intraspecific competition

predation

+ organisms of DIFFERENT species compete with each other for resources ie food.

+ interspecific competition can mean that the resources available to both popualtions are reduced. - this leads to smaller popualtion size due to lack of energy for growth and reproduction.

+ if 2 species are competeing but one is better adapted to its surroundings than the other , the least adapted species will be outcompeted,- it wont be able to live alongside the more adapted species.

+ when organisms of the same species compete with each other for the same resources.

1) when resources are plentiful, the pop. size increases. as the pop. size increases, there will be more organisms competeing for the same amount of food and space.
2) eventually resources such as food and space become limiting, the pop size begins to decrease.
3) a smaller pop. size means theres less competiton for resources, which is better for growth and reproduction , the pop. size grows again

where the predator kills and eats the prey.
the pop. size of predator and prey are interlinked- as one changes, the other changes.

1) prey pop. size increases, more foods for predators, so the predator pop. size increases.
2) as the predator pop. size has increased, more prey is eaten, so the prey pop. size decreases.
3) less food for the predators, so their pop. size decreases.

other factors involved like availabiltiy of food for the prey.

the number of live births each year for every 1000 people in the population

the number of people that die evry year for every 1000 people in the pop.

pop. growth rate / 1000 people each year =

birth rate - death rate

birth rate and death rate fluctuate at a high level, the pop. size stays low

Birth rate is high because theres no birth control or family planning.

High infant mortality.

Death rate is high because theres poor health care and sanitation.

death rate falls, birth rate remains high

pop. size increases rapidly

increased sanitation and healthcare, still little birth control

birth rate falls rapidly, death rate falls slowly

pop. size increases at a slower rate

increased use of birth control

birth rate and death rate fluctuate at a low level

pop. size remains stable but high

birth rate stays lows as there a demand for luxuries so less money for kids

birth rate begins to fall, death rate remains stable

pop. size begins to decrease

death rate remains steady as large amounts of elderly people die