Distributions, Migrations And Dispersal Flashcards
When did the first egg laying mammals (monotremes) arise?
Triassic period
When did modern mammals (placentals and marsupials) first appear?
The Late Cretaceous period
Give some examples of ‘wandering families’:
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)
What is endemicity?
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
What are flowering plants called?
Angiosperms
Why did flowering plants evolve so late?
Nature of fossil evidence: could have been present
Environmental considerations: not suitable until CO2 levels were high enough
Give some advantages of angiosperms:
Tough leathery leaves- drought resistant
Resistant seed coat prevents desiccation
More efficient water conducting vessels
Rapid reproduction
Accelerated speciation- diversity of adaptive types
Why was there such rapid diversification of angiosperms?
Insect-angiosperm co-evolution
Genetic exchange between widely spaced individuals and small populations
What are cosmopolitan taxa/species?
Species that occur over all/most regions of the world
E.g humans
What higher taxa are cosmopolitan?
Insects and grasses
What are widespread taxa?
Species that are common in only suitable habitats in well-defined regions of the world
Give some examples of widespread taxa:
Cacti: widespread in north, central and South America but not found anywhere else
Penguins
Heather
Pine
What is the definition of disjunct distribution/taxa?
Give an example
Species that are found in one place and then found in another completely different place
E.g marsupials
What are endemics?
Give an example
Species found in only one well-defined region, large or small
Finches on individual Galápagos Islands
Red grouse Britain
Rosy periwinkle Madagascar
Eucalyptus Australia
What two countries are considered really important for endemic plant species?
South America and Madagascar
Give an example of climatic relicts and describe it
Arctic spring tail
Glacial retreat led to speciation
Arctic springtail= 2x8 eyelets
Pyrenees springtail= 2x6 eyelets
Why is dispersal and migration important?
2 points
- Successful species multiply and spread
2. Genetic isolation increases speciation
What are the secrets of success for plant dispersal?
- Seeds are resistant to desiccation
- Long distance dispersal
- Many plants have both sexes on the same plant
- Aerial dispersal
- Plants with fruit attracts birds and other animals
- Vegetative reproduction
- Primary producers- self sufficient
- Seeds resistant to fungal diseases
What are the disadvantages of animal dispersal?
- They need to individuals of the opposite sex to breed
- They need a food source to survive
- They may carry parasites and diseases
When is migration most rapid?
When there is continuity of habitat
What are corridors?
Stretches of continuous habitat, land or water that allow migration in both directions
What are barriers?
Patches of unfavourable habitat, e.g oceans such as the English Channel
What are filters?
They have selective corridors, e.g the Pyrenees allow cold tolerant species to disperse
What are bridges? Give an example
They are temporary corridors
E.g beringia allowed the passage between Asia and North America for cold tolerant species
