L4 Tosh - Distributions, migrations and dispersal

Question 1

Define endemicity

Answer 1

the number of families that only occur in that continent. Australia has the highest number as it has been isolated for the longest

Question 2

Modern angiosperms made their way to the northern hemisphere by 95mya. What was the rise in flowering plants accompanied by?

Answer 2

It was accompanied by the reduction in numbers and variety of mosses, horsetails, ferns and cycads

Question 3

Angiosperms dominate the world flora today with 300-400 families and up to 300000 species. Where did they originate, when and how long did it take for them to spread>

Answer 3

They originate in the Paleotropics 135mya, and they radiated world wide in less than 10my.

Question 4

Why was the emergence of flowering plants so late?

Answer 4

Angiosperms were present much earlier than the cretaceous period but there is poor fossilisation in dry uplands.

So DNA evidence from mitochondrial DNA, nuclear and chloroplast genomes.

These suggest a split between gymnosperms and angiosperms in late carboniferous (290mya)

Question 5

What global environmental change allowed the angiosperms to emerge?

Answer 5

The angiosperms emerged at a time when CO2 levels and temperature increased:

Oceanic anoxia, sea floor spreading
Volcanic activity elevated CO2
So changes in global sea levels and atmosphere from ‘superplume’ episode

Question 6

Why was there such a rapid diversification of angiosperms?

Answer 6

1. co-evolution with insects
2. insect pollination was advantageous - genetic exchange between widely spaced individuals
3. advanced pollinators (bees and moths) played major role in the co-evolution and radiation of some plants

(But wasn’t solely to do with insects)

Question 7

What is a cosmopolitan taxa?

Answer 7

A taxa seen everywhere - there are few true examples (humans)

Question 8

What kind of species are cosmopolitan species?

Answer 8

several aniumals and plants travelled with humans - horses, sparros, plantain

few species have the physiology and behaviour to survive e verywhere.

Mainly higher taxonomic ranks

Question 9

Give 4 examples of endemic species and their habitats

Answer 9

1. Finches - individual islands of Galapagos
2. red grouse - Britain
3. Rose Periwinkle - Madagascar
4. Eucalyptus - Australia

Question 10

Where are the highest rates of plant endemicity found?

Answer 10

South America and Madagascar - probably due to the speciation rates here

Question 11

What are evolutionary relicts and Climatic relicts?

Answer 11

A relict (or relic) plant or animal is a taxon that persists as a remnant of what was once a diverse and widespread population

E.g. the thylacine of Tasmania, a relict marsupial carnivore that survived into modern times on an island whereas the rest of its species on mainland Australia had long ago gone extinct

Question 12

Give reasons the reasons that plants are so successful at dispersal

Answer 12

1. Seed resistance - to cold, heat, desiccation, transportation
2. Self fertilisation#
3. Aerial dispersal
4. Primary producers - self sufficient
5. Invasive and opportunistic plants

Question 13

Animal dispersal is most rapid when there is continuity of habitat. Give 4 examples

Answer 13

1. Corridors - stretches of continuous habitat, land or water, allowing migration in both directions
2. Barriers - patches of unfavourable habitats. E.g. the English channel
3. Filters - selective corridors
   E.g. Pyrenees - allows cold tolerant to migrate
4. Bridges - temporary corridors