Biogeography

Question 1

Australia

Answer 1

strange mammal fauna eg monotremes, giant flightless birds (emus)

Question 2

Galapagos land mammals

Answer 2

only galapagos rice rat

Question 3

dominant land mammals in galapagos

Answer 3

herbivorous turtles and iguanas

Question 4

is the environment in the galapagos just not conducive to mammals?

Answer 4

no- once introduced to the galapagos, goats thrived, almost destroying the ecosystem

Question 5

Darwin’s mistake

Answer 5

collected turtles for eating on the voyage, didn’t realise there were many different species of turtles and that he had eaten a new species
Could tell where the turtles came from just from the shape of their shell

Question 6

Endemicity in the galapagos

Answer 6

islands just a few miles apart have same habitats but very different turtle species

Question 7

what is primarily responsible for the distribution of different groups

Answer 7

geographical barriers- oceans and mountains
as opposed to environmental conditions eg species on plains of S America aren’t similar to species on plains of Europe, N America or Africa- they’re similar to things in mountains and forest of S America

Question 8

Wallace’s contribution related to

Answer 8

biogeography

Question 9

What were the biogeographic realms wallace broke the world into

Answer 9

palearctic
nearctic
neotropical
ethiopian
oriental
australian

Question 10

fact that physical barriers to movement controlled distributions suggests

Answer 10

groups of animals and plants, had moved to occupy their present ranges until they couldn’t move

Question 11

dispersal mechanisms

Answer 11

land bridges

oceanic dispersal

Question 12

land bridges

Answer 12

existence of similar species on different land masses

Question 13

Bering land bridge

Answer 13

Russia and Alaska separated by 50 miles water
Geological record of UK shows marine rocks on land- implied sea level could change and/or land could be lifted up- could let land mammals pass what used to be ocean
discovery of ice ages where lots of water locked up in glaciers- explained how sea levels van be vastly reduced to make bridge

Question 14

How can climate change act as a filter on bridges

Answer 14

climate determines how far N/S a species can spread

species that can only inhabit warm climates can’t spread across high-latitude land bridges

Question 15

Paleocene-Eocene thermal maximum

Answer 15

55 m years ago, already warm climate became suddenly much warmer

Question 16

What happened when the poles were subtropical

Answer 16

because high latitudes subtropical, warmth loving species could move north
Meant Beringia and other high latitude land bridges no longer had a climatic filter

Question 17

who moved from asia into europe and n america through beringia/greenland

Answer 17

warmth loving primates
55m years ago
ancestors of horses spread into n america and later spread back across bering bridge into asia, europe and africa

Question 18

what implies the and bridge is v recent

Answer 18

fishes and marine life on either side of the isthmus of panama very similar

Question 19

great American interchange

Answer 19

fossils show that a few million years ago S America was an island continent- different fauna: giant armadillos, rodents, giant flightless birds.
N America: bears, cats, horses etc
Isthmus formed: southern species moved north and N moved S

Question 20

How are the Galapagos colonised without land bridges?

Answer 20

flight

Question 21

Flight mechanisms

Answer 21

birds blown out to se by storms, lost while migrating
Birds travels in flocks so a viable pop can colonise an island at once
Insects also blown long distances
Birds also dispersal vectors- carry seeds in crops/guts, invertebrates on their feet
Fern spores and plant seeds float on wind for long distances

Question 22

What does flight explain

Answer 22

why island fauna often dominated by birds

Mammals outcompete them usually- can’t compete if can’t access the environment

Question 23

Why do birds become large and flightless when access islands

Answer 23

exploit abundant food

Question 24

Water dispersal

Answer 24

species of plant adapted to float e.g. coconut- distributed in tropics all over the world

Question 25

Floating of plants by other means

Answer 25

icebergs trap rocks and soil

Soil trapped in tree roots can also carry seeds

Question 26

Animals that float/swim

Answer 26

tortoises have a lighter weight shell than turtles to move on land- v buoyant
Can survive months without food/water
Crocs good swimmers and can drink saltwater- colonise distant islands

Question 27

What is required for dispersal of animals to be successful

Answer 27

multiple individuals, or a female with a clutch of fertilised eggs

Question 28

Animals that can’t fly/float long distances?

Answer 28

Rafting
trees and vegetation rafts drift long distances so animals clinging can travel too
Works better for lizards than mammals: go long without food and water
Galapagos rice rate anomaly: most offshore island have lizards, but not mammals

Question 29

amphisbaenia

Answer 29

worm lizards
poor candidates for dispersal: live in burrows, don’t swim/float
However they’re widespread- continental drift

Question 30

Pangea evidence

Answer 30

coasts of Africa and S America fit together, geology on either sides of Atlantic matches
Rocks on one coast similar in age and composition to on the other coast
Fossils from the Permian similar in Africa and S America

Hence land masses once joined into one giant continent

Question 31

Seafloor spreading and plate tectonics

Answer 31

Discovery of seafloor spreading and subduction found that ocean crust near mid ocean ridges younger than crust further away
- seafloor splits along mid ocean ridges and new crust generates as crust split apart
Old crust thrown down into the earth in trenches and melted- created conveyer belts which drove continents apart

Question 32

Gondwanaland

Answer 32

200m years ago

S America, Africa and India joined

Question 33

Pangea

Answer 33

250 m ya

All continents united

Question 34

What else does continental drift explain the distribution of

Answer 34

marsupials and flightless birds

Question 35

Problems with CD explanation for dispersal of worm lizards

Answer 35

don’t diversify till after continental breakup (shown by evol tree, made from fossil evidence and molecular clock/data), so distribution can’t be explained by CD
SO must involve dispersal
Must have crossed the Atlantic

Question 36

So how did worm lizards disperse?

Answer 36

Travelling in soil carried by floating vegetation (same as seeds)
Trees- fallen of eroding cliffs, washed out to sea by rivers or tsunamis, could have carried them in their roots

Question 37

Ratites

Answer 37

fossils and molecular data also reject CD as explanation for dispersal
Oldest fossils of ratites don’t appear until Palaeocene (after CD, after Gondwana broken up) And they can fly.
Ratites flew then evolved large, flightless forms to take adv of niches left by Dino extinction

Question 38

Mammals

Answer 38

most are recent, radiate after cretaceous in response to Dino extinction
S America was a island continent till Isthmus of Panama formed
Madagascar and Aus isolated since the cretaceous
SO inhabitants had to cross water

Question 39

Fossil marsupials

Answer 39

Oldest not from Gondwana, instead Cretaceous of China and N america
First appearance in southern hemisphere is in the paleocene of s america
Immigrated when dinos went extinct maybe by rafting
Recent spread of marsupials from N america to S america to Australia = dispersal