populations (19.4)

Question 1

define population

Answer 1

• a group of organisms of one species
• living in the same area, at the same time

Question 2

define community

Answer 2

all of the populations of different species in an ecosystem

Question 3

define ecosystem

Answer 3

• unit containing the community of organisms
• & their environment,
• interacting together

Question 4

Identify & state the factors affecting the rate of population growth for a population of an organism

Answer 4

Food supply
* more food available = more likely populaton’s growth.

Competition
* organisms compete for resources they need to survive & reproduce.
* plants compete for light, space, water, mineral ions.
* animals = space, water, food, mates.
* presence of new competitors affects population size.

predation
* population of prey increases = predators increase too
* as predator population increases, prey’s population decreases.
* if predator population removed= size of prey population increase until no. of prey reached max the environment could support; the prey population would start to decrease.

disease
* presence of pathogen affects popualtions growth rate
* may decrease in size due to illness.

Question 5

Explain the factors that lead to each phase in the sigmoid curve of population growth; populsyion growing in an environment w limited resources
(lag, exponential [log], stationary, death)

Answer 5

Lag phase
* population increasing slolwly
* few individuals; rate of reproduction low

Exponential (log) phase
* increasing no of individuals reproducing; population size increases more & more quickly.
* plenty of resources available for no of individuals. population able to rapidly reproduce; environment has enough resources.

Stationary phase
* population size levels off, stays fairly stable (birth & deate rates in equilibrium)
* population size limited by availability of resources - shelter, food, water.
* resources prevent population size from increasing = limiting factors
* population reaches carrying capacity.

Death phase
* rate at which dying is faster then reproductive rate; population size drops; population used up too many resources of environment; can be no longer supported.
* waste products can also build up to toxic levels (population of microorganisms)