6.6.1 What determines population size

Question 1

Define Carrying capacity.

Answer 1

The maximum population size that can be maintained over a period in a particular habit

Question 2

Define Limiting factor.

Answer 2

The factor whose magnitude slows down. the rate of a natural process

Question 3

What determines the size of a population?

Answer 3

The balance between the death rate and the rate of reproduction.

Question 4

What happens in the lag phase of population growth?

Answer 4

Few individuals that are acclimatising to their habitat. The rate of reproduction is low and growth in population size is slow.

Question 5

What happens in the Log phase of population growth?

Answer 5

Resources are plentiful, reproductions happens quickly and rate of reproduction exceeds mortality. Population size increases rapidly.

Question 6

What happens at the Stationary phase of population growth?

Answer 6

Population is at carrying capacity of the habitat. The rates of reproduction and mortality are equal. Population size stays stable, may fluctuate to small variations.

Question 7

Define density independent limiting factors.

Answer 7

They are limiting factors that act just as strongly, irrespective of the population size.

Question 8

Give an example of a density independent limiting factors.

Answer 8

An example would be temperature, Low temperatures may kill the same proportion of the population irrespective to its size.

Question 9

Define density dependent limiting factors.

Answer 9

Where factor influences population more strongly as population rises

Question 10

Give examples of density dependent limiting factors.

Answer 10

Availability of resources, like food, water, etc
As population size increases so does the intensity of competition for resources.

Question 11

Define k-strategists.

Answer 11

Species whose population size is determined by the carrying capacity. Limiting factors exert a more significant effect as population size gets closer to the carrying capacity, causing population size to gradually. level out.

Question 12

What are examples of k-stratigists?

Answer 12

Birds, large mammals (humans, lions, elephants) and large plants.

Question 13

What are characteristics of k-strategists?

Answer 13

Low reproductive rate, slow development, late reproductive age, long lifespan and large body mass.

Question 14

Define r-strategists.

Answer 14

Species that are adapted to a different type of population growth, where the population size increases so quickly that it can exceed the carrying capacity before the limiting factors start to have an effect.This causes resources to run out so individuals cannot reproduce, build up of waste products may start to poison the species and they begin to die.

Question 15

What happens at the boom and bust phase of population growth.

Answer 15

Where the population exceeds the carrying capacity (the boom) and eventually resources run out, and excess waste products kill (the bust)

Question 16

What are examples of r-strategists?

Answer 16

Mice, insects, spiders and weeds.

Question 17

What characteristics do r-strategists share?

Answer 17

High reproductive rate, quick development, young reproductive age, short life span, small body mass.

Question 18

What is the most important influence on population growth for r-strategists?

Answer 18

The physical rate at which individuals can reproduce.

Question 19

What does quick population growth mean between r-strategists and k-strategists?

Answer 19

Pioneer r-strategists species colonise a disturbed habitats before k-strategists, then disperse to other habitats once limiting factors start to have an effect.

Question 19

List three biotic and two biotic factors which could act as limiting factors.

Answer 19

Biotic- Competition for mates, predation, and parasitism.
Abiotic- Temperature and PH

Question 19

During each of the following, indicate which is higher- death rate or reproduction rate.
a) Lag phase
b) Log phase
c) Stationary phase

Answer 19

a) Reproduction rate
b) Reproduction rate
c) death rate and reproduction rate level each-other out.

Question 19

Explain the connection between limiting factors and carrying capacity.

Answer 19

When a habitat reaches it’s carrying capacity, it cannot support a larger population as limiting factors limit population growth. Some limiting factors work independently to the carrying capacity, and will affect the population the same regardless to the population size such as temperature, whereas other limiting factors are population dependent and will affect the population more strongly if it is at carrying capacity, such as availability of resources.

Question 19

Explain the difference between r- and k-strategists.

Answer 19

r- Strategists adopt to a rapid increase of population size that exceeds the carrying capacity, and creates a bust (due to build of waste products killing) whereas k-strategists adapt to a population size that is determined by carrying capacity, where limiting factors gradually level out population size.