3.2 Origins of Biodiversity

Question 1

define evolution

Answer 1

the cumulative, gradual change in the genetic composition of a species over many successive generations, ultimately giving rise to species different from the common ancestor

Question 2

natural selection notes

Answer 2

darwins notes noted:
- pop show variations (i.e. not all individuals are the same)
- pop. always over-reproduce to produce excess offspring
- not enough resources available for all offspring: competition for resources

• due to variation of species some are fitter than others → those will have an advantage and will reproduce more successfully than individuals who are less fit
• those that survive have genes that give them an adaptive advantage
• genes are inherited by offspring and passed on to the next gen.
• over time there is a change in the gene pool, leading to the formation of new species

Question 3

define speciation

Answer 3

the formation of new species when populations of a species become isolated and evolve differently

Question 4

geographical isolation

Answer 4

a physical barrier that leads to populations becoming separated, eventually leading to speciation

causes include plate activity, the formation of mountains, seas, lakes, rivers and deserts

Question 5

plate tectonics

Answer 5

the movement of eight major and several minor internally rigid plates of the Earths lithosphere in relation to each other and to the partially mobile asthenosphere below.

Question 6

list 3 physical factors that might separate populations

Answer 6

• mountain ranges
• bodies of water
• natural events

Question 7

temporal isolation

Answer 7

species that live lives during different times of day, and therefore dont interbreed

Question 8

behavioural isolation

Answer 8

courtship rituals between two species vary

Question 9

constructive plate margins

Answer 9

plates move apart

Question 10

destructive plate margins

Answer 10

plates move together

Question 11

collision plate margins

Answer 11

plates collide

Question 12

collision of plates can lead to:

Answer 12

• uplift and mountain formation → form physical barrier which isolates populations
  + also creates new habitats, promoting biodiversity (adaptation to new habitats the occurs through natural selection)
• spread of species through the creation of land bridges → mixing of gene pools and possible hybridisation

Question 13

plate activity can:

Answer 13

• create new islands usually through volcanic activity
  → can lead to adaptations to fill new habitats/niches
• movement of plates → evolutionary changes, for example the northward movement of the Australian plate

Question 14

mass extinction definition

Answer 14

a period in which at least 75% of the total number of species on the Earth at the time are wiped out.

Question 15

how many mass extinctions have there been

Answer 15

5

Question 16

the Sixth Extinction

Answer 16

• population of many species decline
• related to human activity
• species unable to adapt

Question 17

why is the Sixth Extinction different?

Answer 17

caused by a single species (humans):
- climate change
- deforistation (habitat loss)
- poaching
- hunting
- overfishing

Question 18

2 phases of the Sixth Extinction

Answer 18

1: began when the first modern humans began to disperse to different parts of the world about 100000 years ago

2: about 10000 years ago when humans turned to agriculture to grow food

(development of agriculture and clearance of native ecosystems accelerated pace of extinction)

Question 19

possible causes of mass extinctions

Answer 19

• asteriod impact
• volcanic activity leading to climate change
• extreme temperature changes
• sea level change due to glacier formation