3.8 Threats to Biodiversity

Question 1

can populations recover after being reduced to a low level by overexploitation?

Answer 1

yes

Question 2

some species have a naturally low genetic diversity, yet…

Answer 2

remain viable

Question 3

the bottleneck effect

Answer 3

an evolutionary event in which a significant percentage of a population/species is killed or otherwise prevented from reproducing

Question 4

result of the bottleneck effect

Answer 4

small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change

Question 5

why can the bottleneck effect be critical for small populations?

Answer 5

inbreeding resulting from a decline in individuals able to reproduce can result in poor reproductive rates

Question 6

cause of habitat fragmentation

Answer 6

the clearing of habitats

Question 7

degradation of the edges of habitat fragments results in what, and why is this?

Answer 7

• increased competition between species, and reduced biodiversity
• because the fragments are becoming smaller

Question 8

more isolated and smaller habitat fragments exhibit…

Answer 8

a lower species diversity

Question 9

how to remedy widespread habitat fragmentation?

Answer 9

isolated fragments can be linked with habitat corridors

Question 10

what do habitat corridors allow?

Answer 10

the movement of animals between fragments

Question 11

habitat corridors increases… (2)

Answer 11

• access to food
• choice of mate

Question 12

habitat corridors may lead to

Answer 12

the recolonisation of small fragments after local extinctions

Question 13

non-native species stages (3)

Answer 13

• introduced species
• naturalised species
• invasive species

Question 14

introduced species

Answer 14

species that humans have moved either intentionally or accidentally to new geographic locations

Question 15

naturalised species

Answer 15

introduced species which have become established within wild communities

Question 16

invasive species

Answer 16

naturalised species that spread rapidly and eliminate native species - reducing species diversity

Question 17

in their new geographic locations, invasive species may be free of…

Answer 17

the predators, parasites, pathogens and competitors that limit their population in their natural habitat

Question 18

activities that may be carried out by invasive species (3)

Answer 18

• prey on native species
• outcompete native species for resources
• hybridise with native species