Chapter 6.6-Population and sustainability

Question 1

What are the three stages in population growth of a species?

Answer 1

• lag phase:there many only be a few individuals, which are still acclimatising to their habitat. Rate of reproduction is low and the growth in population size is slow.
• log phase: resources are plentiful, and conditions are good. Reproduction can happen quickly, with the rate of reproduction exceeding mortality. Population size increases rapidly
• stationary phase: population size has reach its carrying capacity of the habitat. Rate of reproduction and mortality are equal. Population size remains relatively stable

Question 2

What is meant by the carrying capacity(k)?

Answer 2

the maximum population size that can be maintained over a period in a particular habitat

Question 3

What is meant by limiting factors?

Answer 3

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

Question 4

What are density independent limiting factors and name two examples?

Answer 4

• factors act just as strongly, irrespective of the size of the population
• low temperatures and light levels

Question 5

What are density dependent factors and name two examples?

Answer 5

• factor influences population size more severely as the population size increases
• availability of resources like food and predation

Question 6

Name two other biotic limiting factors

Answer 6

• disease

- competition for resources

Question 7

Name two other abiotic limiting factors?

Answer 7

• pH

- humidity

Question 8

What are k-strategists?

Answer 8

• species whose population size is determined by the carrying capacity (limiting factors)
• as the species population size increases, the effect of the limiting factors have a greater effect
• population size eventually levels out (stationary phase)

Question 9

What are the main characteristics of k-strategists?

Answer 9

• low reproductive rate
• slow development
• later reproductive age
• long lifespan
• large body mass

Question 10

What type of organisms are usually k-strategists and name some examples?

Answer 10

• larger mammals

- birds, humans, elephants and larger plants etc

Question 11

What are r-strategists?

Answer 11

• species which try to outmanoeuvre the limiting factors
• population size increases quickly and it exceeds the theoretical carrying capacity and then the limiting factors start to have an effect
• one the carrying capacity has been exceeded, there are no longer enough resources for survival and there is a build up of waste products
• organism being to die entering a death phase

Question 12

What are the main characteristics of r-strategists?

Answer 12

• high reproductive rate
• quick development
• young reproductive age
• short life span
• small body mass

Question 13

What type of organisms are usually r-strategists and and name some example?

Answer 13

• smaller organisms
• mice
• insects
• spiders

Question 14

What type of strategists colonise a disturbed habitat first, r or k-strategists?

Answer 14

• r-strategists

- r-strategists population can grow rapidly as they have short generation times, such as bacteria and pioneer species

Question 15

Describe predator-prey relationship?

Answer 15

Cyclic fluctuations

1. When predator population gets bigger, more prey are eaten
2. The prey population gets smaller, leaving less food for the predators
3. With less food, fewer predators can survive and their population size reduces
4. With fewer predators, fewer prey are eaten, and their population size increases
5. With more prey, the predator population gets bigger, and the cycle starts again

Question 16

What is intraspecific competition?

Answer 16

competition between individuals of the same species

Question 17

What is interspecific competition?

Answer 17

competition between individuals of different species

Question 18

What does intraspecific completion do to the population size of a species?

Answer 18

• keeps the population size relatively stable (stationary phase)
• if pop size drops, then competition reduces and the pop size increases
• if pop size increases, competition increases and the pop size drops

Question 19

What is the competitive exclusion principle resulting from interspecific competition?

Answer 19

• more overlap between niches= more intense competition for limited resources
• no 2 species can occupy the same niche indefinitely when resources are limited

Question 20

What is some issues with the competitive exclusion principle?

Answer 20

• extinction of one species is not inevitable

- there are lots of different variables that affect the population size, not just competition for resources

Question 21

In predator-prey relationships, why are population crashes of both predator and prey (low population size) important?

Answer 21

important for evolution as these select individuals who are better adapted to the habitat

Question 22

What is preservation?

Answer 22

maintenance of habitats and ecosystems in their present condition, minimising human impact

Question 23

What is conservation?

Answer 23

maintenance of biodiversity, including diversity between species, genetic diversity within species, and maintenance of a variety of habitats and ecosystems

Question 24

Whats the difference between preservation and conservation?

Answer 24

preservation keeps species and habitats as they are now whereas conservation is a more active process which aims to maintain and/or improve biodiversity