24.1 Populations and Sustainability

Question 1

What is a limiting factor?

Answer 1

The environmental resource or constraint that limits growth.(prevents further growth of population.

Question 2

What is the growth curve also known as?

Answer 2

Signoid population growth

Question 3

What are the stages of the population growth curve?

Answer 3

• Phase 1- period of slow growth
• Phase 2- period of rapid growth.
• Phase 3- a stable state.

Question 4

Describe Phase 1 of population curve.

Answer 4

• Small numbers of individuals initially present.
• Reproducing increases population.
• Birth rate is higher than death rate.

Question 5

Describe Phase 2 of population curve.

Answer 5

• As number of breeding individuals increase.
• Populatuon multiplies exponentially.
• No constraints to limit population explosion.

Question 6

Describe Phase 3 of population curve.

Answer 6

• Further population growth prevented by constraints.
• Population size fluctuates but overall remains stable.
• Birth rate approximately equal to death rate.
• Slight increases and decrease caused by fluctuations in limiting factors e.g predators.

Question 7

What are examples of limiting factors?

Answer 7

• Competition between organisms for resources.
• Disease
• The build-up of toxic byproducts of metabolism.

Question 8

What are two types of limiting factors and give examples.

Answer 8

• Abiotic(Non living factors) temperature,light, ph, humidity, availability of ph or water
• Biotic (Living factors) predators, competition,disease

Question 9

What is carrying capacity?

Answer 9

The maximum population size an environment can support.

Question 10

What is Immigration?

Answer 10

• The movement of individual organisms into a particular area, increases population size.
• For example Christmas Island crabs migrate each year from forest to coast to reproduce, increasing coastal populations of red crabs.

Question 11

What is emigration?

Answer 11

The movement of individual organisms away from a particular area, decreases population size.

Question 12

What are density independent factors? and give examples

Answer 12

• Factors that have effect on whole population regardless of population size.
• eg earthquakes,fires,storms, volcanoes

Question 13

Suggest and explain a social, cultural or religious pressure which may affect the size of a population.

Answer 13

• Pressure- some religions discourage contraception.
• effect on birth rate/death rate-This increases birth rate.
• effect on population- Increasing population.

Question 14

What does the future size of a population depend on?

Answer 14

The number of women of child bearing age.

Question 15

Describe what happens during a period of exponential growth?

Answer 15

• Population doubles in size.
• Increases by a fixed proportion.
• Each time a fixed interval of time elapse.

Question 16

What is the result of inter specific competition?

Answer 16

• When 2 or more species compete for same resource.
• This interaction results in reduction of resources for both populations.
• Organism has less energy for growth and reproduction.
• Resulting in smaller populations, than if only one species was present.

Question 17

What is competitive exhaustive principle?

Answer 17

• When 2 species compete for limited resources.

- The one that is better adapted or uses resources more efficiently will outcompete/ eliminate the other.

Question 18

What is an important example of inter specific competition we have to know?

Answer 18

• Red and grey squirrels.
• Grey squirrels can eat wider range of food than red.
• Grey is larger, can store more fat.
• Increases chance of survival, and ability to reproduce.
• Increasing grey squirrel population further reduces food supply available to red squirrels.
• Reducing ability to survive and reproduce.

Question 19

In infra specific competition what determines population size?

Answer 19

• The availability of the resource, the greater the resource the larger the population that can be supported.
• This results in fluctuations in the number of organisms present in a particular population over time.

Question 20

Describe the effects of competition on population overtime?

Answer 20

• When resource is plentiful in habitat(food/space).
• All organisms have enough resources to survive and reproduce.
• Results in population increase.

Question 21

Stage 2 intra specific population?

Answer 21

• As a result of increased population.
• More individuals share resource available (food/space).
• Resources limited so not enough available for organisms to survive.
• Population decreases in size.

Question 22

Stage 3 intra specific competition?

Answer 22

• Less competition exists
• As smaller Population means less organisms are competing for same resource.
• This means more organisms can survive and reproduce.
• Resulting in population growth.
• Stages repeat

Question 23

Oak tree saplings compete for light and water, suggest the population of oak trees will vary overtime?

Answer 23

• Individuals which grow fastest/ better will survive.
• As saplings grow taller they reduce light for other saplings.
• Results in death of other saplings.

Question 24

What is predation?

Answer 24

When a predator kills and eats prey.

Question 25

How have predators evolved to be efficient at capturing prey?

Answer 25

• Sudden burst of energy
• Stealth
• Fast reactions

Question 26

How have prey evolved to avoid capture?

Answer 26

• Camouflage
• mimicry
• Defence mechanisms like spines.

Question 27

What is the relation between predator- prey population size?

Answer 27

• They are interlinked.
• As population for one organism changes, it causes change in size of other.
• Results in fluctuations in size of both populations.

Question 28

Describe the graph on predator and prey relationships.

Answer 28

The peak and trough in the size of prey population are mirrored by peak and trough in the size of the predator population after a time delay.

Question 29

Describe stage 2 of predator-prey relationship graph.

Answer 29

• Prey population increase so more food for predators.
• More chance of survival, and an increase in ability of reproduction
• Results in increase in predator population.

Question 30

Describe stage 2 of predator-prey relationship graph

Answer 30

• Increased predator population eats more prey.
• Decline in prey population.
• Death rate of prey population higher than birth rate.

Question 31

Describe stage 3 of predator-prey relationship graph

Answer 31

• Reduction in prey population can not support predator population.
• Intra specific competition for food increases.
• Resulting in decrease in size of predator population.

Question 32

Describe stage 4 of predator-prey relationship graph.

Answer 32

• Reduce in predator population, results in less prey being killed.
• More prey survive and reproduce.
• Increasing prey population(cycle repeats again).

Question 33

Is the the link between predator and prey simple as described?

Answer 33

• No that is rare.

- Other factors influence population size, eg seasonal changes, change in abiotic factors.

Question 34

What is an interdependence between prey and predator?

Answer 34

When predator feeds on only one type of prey.

Question 35

Explain the changes in the populations of the lynx and how that occurred overtime.

Answer 35

• Hare Population initially increases, due to low number eaten by lynx.
• Large hate populations now provides more food for lynx.
• So more lynx can survive and reproduce.
• Increasing lynx population
• More lynx increases predation of hares.
• So hare population decreases.
• No longer enough food to sustain lynx population.
• Increasing lynx death rate so lynx population decreases. cycle begins again.