Distributions, Migrations And Dispersal

Question 1

When did the first egg laying mammals (monotremes) arise?

Answer 1

Triassic period

Question 2

When did modern mammals (placentals and marsupials) first appear?

Answer 2

The Late Cretaceous period

Question 3

Give some examples of ‘wandering families’:

Answer 3

Shrews
Squirrels 
Hamsters and voles 
Hares and rabbits 
Bears 
Dogs 
Cats 
Mustelids (except Australia)
Bovids (except S America and Australia)
Rats and mice (except N and S America)

Question 4

What is endemicity?

Answer 4

The number of endemic families x100/total number of families

If a land mass has 100% endemicity that means all those families occur there and nowhere else

Question 5

What are flowering plants called?

Answer 5

Angiosperms

Question 6

Why did flowering plants evolve so late?

Answer 6

Nature of fossil evidence: could have been present

Environmental considerations: not suitable until CO2 levels were high enough

Question 7

Give some advantages of angiosperms:

Answer 7

Tough leathery leaves- drought resistant

Resistant seed coat prevents desiccation

More efficient water conducting vessels

Rapid reproduction

Accelerated speciation- diversity of adaptive types

Question 8

Why was there such rapid diversification of angiosperms?

Answer 8

Insect-angiosperm co-evolution

Genetic exchange between widely spaced individuals and small populations

Question 9

What are cosmopolitan taxa/species?

Answer 9

Species that occur over all/most regions of the world

E.g humans

Question 10

What higher taxa are cosmopolitan?

Answer 10

Insects and grasses

Question 11

What are widespread taxa?

Answer 11

Species that are common in only suitable habitats in well-defined regions of the world

Question 12

Give some examples of widespread taxa:

Answer 12

Cacti: widespread in north, central and South America but not found anywhere else

Penguins

Heather

Pine

Question 13

What is the definition of disjunct distribution/taxa?

Give an example

Answer 13

Species that are found in one place and then found in another completely different place

E.g marsupials

Question 14

What are endemics?

Give an example

Answer 14

Species found in only one well-defined region, large or small

Finches on individual Galápagos Islands
Red grouse Britain
Rosy periwinkle Madagascar
Eucalyptus Australia

Question 15

What two countries are considered really important for endemic plant species?

Answer 15

South America and Madagascar

Question 16

Give an example of climatic relicts and describe it

Answer 16

Arctic spring tail

Glacial retreat led to speciation

Arctic springtail= 2x8 eyelets
Pyrenees springtail= 2x6 eyelets

Question 17

Why is dispersal and migration important?

2 points

Answer 17

1. Successful species multiply and spread

2. Genetic isolation increases speciation

Question 18

What are the secrets of success for plant dispersal?

Answer 18

1. Seeds are resistant to desiccation
2. Long distance dispersal
3. Many plants have both sexes on the same plant
4. Aerial dispersal
5. Plants with fruit attracts birds and other animals
6. Vegetative reproduction
7. Primary producers- self sufficient
8. Seeds resistant to fungal diseases

Question 19

What are the disadvantages of animal dispersal?

Answer 19

1. They need to individuals of the opposite sex to breed
2. They need a food source to survive
3. They may carry parasites and diseases

Question 20

When is migration most rapid?

Answer 20

When there is continuity of habitat

Question 21

What are corridors?

Answer 21

Stretches of continuous habitat, land or water that allow migration in both directions

Question 22

What are barriers?

Answer 22

Patches of unfavourable habitat, e.g oceans such as the English Channel

Question 23

What are filters?

Answer 23

They have selective corridors, e.g the Pyrenees allow cold tolerant species to disperse

Question 24

What are bridges? Give an example

Answer 24

They are temporary corridors

E.g beringia allowed the passage between Asia and North America for cold tolerant species