Topic 6 - Populations And Communities

Question 1

What is a population

Answer 1

A group of organisms of the same species living in a particular area

Question 2

What are the 4 distinct phases of Population growth

Answer 2

Lag phase
Exponential phase
Stationary phase
Decline phase

Question 3

What is the Lag Phase in population growth

Answer 3

This is a strange when nutrient assimilation takes place involving the bacteria activating genes and producing the appropriate enzymes to metabolise a particular food substrate

Question 4

What is the exponential phase in population growth

Answer 4

This is when there is no restriction of growth and bacteria divides exponentially

Question 5

What is the stationary phase in population growth

Answer 5

This is the stage when food supplies may begin to become limiting so the number of new individuals produced falls

Question 6

What is the decline phase in population growth

Answer 6

This is when the death rate exceeds the birth rate and the population declines, possibly due to accumulation of waste or nutrient supply running out

Question 7

What is the biotic potential

Answer 7

The maximum rate of growth as seen in the exponential phase

Question 8

What is environmental resistance

Answer 8

The restriction by the environment on the population reaching its maximum growth rate and its biotic potential

Question 9

What are abiotic factors

Answer 9

Factors in the chemical or physical environment and are losselt referred to as non-living

Question 10

What are biotic factors

Answer 10

The effects of other organisms whether the same or other species

Question 11

What is the carrying capacity

Answer 11

The maximum number of a population that the ecosystem can support

Question 12

What are renewable resources

Answer 12

The nutrients that were there at the start of the investigation were not replaced

Question 13

What is intraspecific competition

Answer 13

Competition between members of the same species

Question 14

What is interspecific competition

Answer 14

Competition between members of a different species

Question 15

What are some commons features of a predator-prey graph

Answer 15

The predators peaks and troughs lag behind the preys peaks and troughs
The length of the predator cycle is usually similar to the length of the prey cycle
The number of predators is normally significantly lower than the number of prey individuals

Question 16

What are r-selected species

Answer 16

Opportunistic Individuals or groups that tend to grow very quickly and increase in population when conditions are ideal

Question 17

What are k-selected species

Answer 17

Stable populations and the population size usually remains at or close to the carrying capacity of the species

Question 18

What are some features of an r-selected species

Answer 18

Small body size
Short lived
Reproduce rapidly
Little parental care
Population size variable
Low competitive ability
Not specialised
Inhabit unstable habitats

Question 19

What are some features of K-selected species

Answer 19

Large body size
Long life cycle
Few offspring
Large amount of parental care
Low dispersal ability
High competitive ability
Highly specialised
Occur in stable habitats

Question 20

What is a parasite

Answer 20

An organism that lives in or on another organism benefiting from jr and causing it harm over an extended period of time

Question 21

How do Parasites differ from predators

Answer 21

The parasite lives in or on the host
The parasite causes harm to the host over an extended period of time
The parasite is usually smaller than the host
The parasite seldom kills the host

Question 22

What is mutualism, and give an example

Answer 22

The interaction where both partners benefits, Lichens between Fungi and green algae

Question 23

What is a pest species

Answer 23

A species that damages a valuable/ commercial crop species, causing economic damage

Question 24

What does biological control involve

Answer 24

Deliberately introducing an organism that will target and cause harm to a pest

Question 25

What are some advantages of effective biological control processes

Answer 25

There is no chemical damage to the environment, reducing bioaccumulation
Biological control targets only the pest species
The develop,end of resistance by the pests is unlikely
Pest resistance is unlikely
Biological control needs little additional action and saves money on the continuing use of pesticides

Question 26

What are some disadvantages of effective biological control processes

Answer 26

The pest is unlikely to be totally eliminated, which could cause a pest resurgence
It will only work well if the control species can adapt well to the ecosystem
The introduced species may outcompete native species

Question 27

What is a community

Answer 27

The sum total of all populations in a particular area

Question 28

What is an ecosystem

Answer 28

The community plus its physical environment

Question 29

What is succession

Answer 29

The term used to describe the changes over time in ecosystems

Question 30

when does primary succession occur

Answer 30

On newly formed, barren substrates that have not been previously colonised

Question 31

What is the first stage of primary succession

Answer 31

The appearance of colonising pioneer species

Question 32

What increases and decreases and succession develops

Answer 32

Soil depth ,soil fertility and plant biomass increases
Plant diversity initially increases but tends to decrease towards the end

Question 33

What is the climax community

Answer 33

The stable end of a succession which is in equilibrium with the environment

Question 34

What is the second stage of succession

Answer 34

Mosses grow in thin soils that develop in rock crevices

Question 35

What is the third stage of succession

Answer 35

Plants grow deeper in the soil formed by decomposition of earlier pioneer species

Question 36

What is the fourth stage of succession

Answer 36

Shrubs and small trees develop in deeper soil. Diversity is high as trees do not form a compete canopy

Question 37

What is the final stage of succession

Answer 37

Soil depth reaches maximum and larger trees begin to outcompete the smaller trees. Diversity drops as few species can survive

Question 38

What are some common features of primary succession

Answer 38

They are predictable in pattern
The abiotic environment becomes less hostile
The height and biomass of vegetation increases
Communities become increasing complex
Communities in later stages of the succession are usually more stable than in earlier seres