Population Size

Question 1

What is biological interaction ?

Answer 1

The effect organisms in a community have on each other.

consumption, competition

Question 2

Define a mutualistic relationship

Answer 2

Where both species benefit from the relationship

One species may be obligate- require other species
N2 fixation in plants

Question 3

Define commensalism

Answer 3

Where one species benefits and the other is unaffected

In reality, interaction unlikely to ever be neutral.

Question 4

What is amensalism ?

Answer 4

Where one organism is not affected whilst the other is negatively affected

Question 5

Define competition ?

Answer 5

An interaction between organisms in which the fitness of one is lowered by the presence of another

Question 6

What is neutralism ?

Answer 6

Interaction between organisms where there is no effect on either species,
Very rare

Question 7

Define Antagonism.

Answer 7

Where one species benefits, the other is disadvantaged in some way.

Question 8

Give an extreme form of mutualism.

Answer 8

Symbiosis,

Close and long-term interaction between two species.

Question 9

Give an example of commensalism.

Answer 9

Remora living off a shark

Question 10

Give an example of amensalism.

Answer 10

Penicillium which secrete chemicals to kill nearby bacteria.

Question 11

What is interference competition ?

Answer 11

Direct interference with others for foraging, reproduction, survival

Question 12

What is exploitation competition ?

Answer 12

Indirect use of resources which depletes the availability for other species

Question 13

What is the competitive exclusion principle, Gause’s law ?

Answer 13

2 species competing for the same resource cannot coexist

One species will adapt or die out.

Question 14

What is apparent competition ?

Answer 14

Indirect competition, between 2 species preyed upon by the same predator.
If one population increases there will be a decrease in predation on the other

Question 15

Which is more fierce, interspecific or intraspecific competition ?

Answer 15

Intraspecific competition between same species

Question 16

Give 2 species which exhibit neutralism

Answer 16

Very rare in nature

Lactobacillus and streptococcus

Question 17

Give some examples of antagonism in nature

Answer 17

Predation, parasitism, herbivory, cannibalism.

Question 18

What is predation ?

Answer 18

When one organisms captures the biomass of another

Question 19

What does predation influence in an ecosystem ?

Answer 19

Distribution, abundance and diversity of species

Question 20

What is a keystone predator ?

Answer 20

Species which have a DISPROPORTIONALLY LARGE IMPACT on their environment relative to their abundance

Question 21

What is predator mediated coexistence ?

Answer 21

Where the predator feeds on the most abundant prey item, preventing one species from becoming dominant, enabling more species to co-exist.

Question 22

How can a predator have a negative impact on a population ?

Answer 22

If a predator feeds preferentially on a competitively inferior prey species, dramatic decrease.
.

Question 23

How can an unfavourable environment, impact prey-predator relationships

Answer 23

If prey in a stressed environment, predation will further reduce the already struggling population size and reduce species richness

Question 24

What does population size depend on ?

Answer 24

Resource availability

Food, nesting sites, refuges

Question 25

Define bottom up control.

Answer 25

Where the resources at the bottom of the system control the predators above

Question 26

Define top down control.

Answer 26

Where the predators at the top of the system influence the prey below them.

Question 27

Describe predator-prey cycles

Answer 27

Predators consume prey
Prey populations decrease, less for predators to eat
Predator population decreases
Prey population has less pressure so begins to increase
Cycle begins again

Question 28

What are the assumptions of the Lotka-Volterra deterministic models used to predict predator prey cycles ?

Answer 28

1. Prey population find ample food at all times
2. Food supply of the predator population depends entirely on the prey populations
3. Rate of change of population is proportional to its size
4. Environment does not change in favour of one species and the genetic adaption is sufficiently slow.

Question 29

Why does the Lotka-Volterra model have significant problems ?

Answer 29

The cycling it predicts is not common in nature

Question 30

What control are most populations affected by, bottom up or top down ?

Answer 30

Both

Question 31

What also plays a key role in predator-prey cycles ?

Answer 31

Parasites

Question 32

Give an example of amensalism

Answer 32

Penicillium secreting chemicals which kill nearby bacteria

No impact on the Penicillium, negative impact on the bacteria

Question 33

Describe the results of Charles Krebs field experiment and what this means for bottom up and top down control.

Answer 33

Used 9, One km blocks of forest
Changed conditions- excluded predation, gave supplementary food, increased plant abundance
Monitored hare populations at 9 sites
Ran for 8 years

Found population are affected by Bottom up and top down control.

Question 34

What did Charles krebs experiment show about bottom up control ?

Answer 34

Bottom up control reliant on resource quality not quantity

Supplementary food increased hare population 3 fold
QUALITY

Fertiliser to increase plant bio mass did not impact hare numbers- QUANTITY

Question 35

In Charles Krebs experiment which site gave the most dramatic increase in hare population ?

Answer 35

The site where predators were excluded and supplementary food was provided
(11 fold increase in hare density)