Examples of how animals interact with each other
Parasitic
Mutualistic (everyone has something to gain)
Define co evolution
Occurs when selection pressures on one species are influenced by the evolution of another
Types of co evolution
Inter-specific competition
Exploitation - predation and parasitism
Mutualism
What happens when competition occurs together
Displacement
May partition resources
Two types of competition
Sympathy (together)
Allopatry (seperated)
Define character displacement in allopatry
Occurs alone
Eg marine mud snails
Standard deviations overlap
Define character displacement in sympatry
The standard deviations vary more
When species occur together, the character size is displaced (eg large do well and small do well but the middle don’t as they are facing too much competition)
True or false: diet separation is greater in allopatry
False
Diet speration is greater in sympatry
Example of exploitation co evolution
Cuckoos
Brood parasites breeding system (they lay their eggs in the nests of other species)
Arrive in N.Europe in April
Set up home range on suitable habitat
How does the cuckoo get the egg in the nest
Swallows the ring warbler egg and then lays one egg in the nest within a small amount of tume as it doesnt want to be caught at the nest
Around 15 eggs per season
What is a typical host of cuckoos eggs
Reed warbler nest found in. Reed beds/marshes
What happens when the cuckoo hatches
Removes competition on day one
How long does it take the cuckoo for them to be ready to flee
3 weeks as they don’t fit in the nest anymore
“Arms race” for co-evolution.
There should be strong selection pressures on host to reject cuckoo
String selection on cuckoo to “fool” host
Have cuckoos evolved?
Sometimes host rejects cuckoo eggs
Lay eggs that mimic host eggs
Main host of cuckoos
Reed warblers (Reed bed)
Dunnocks (farmland)
Meadow pipits (moorland)
Who came up with the model egg experiment
Davies and Brooke
What happens when you put eggs in that don’t look like hosts
Birds usually abandon eggs
Exception to Davies and Brooke model
Dunnock (lays blue eggs) and cuckoo lays brown spotty eggs
Other evidence for co evolution
If you put cuckoo eggs in unsuitabl enviro, they don’t discriminate (have never had this experience)
Icelandic meadow pipits do not discriminate as there is no cuckooos in Iceland so have never been hosts
Why do dunnocks accept cuckoo eggs and not discriminate?
May be new hosts
Azure winged magpie (new host) also don’t discriminate and low rejection
Other adaptations to parasitic breeding
Egg:
Mimicry
Relatively thick shell for size to prevent host removal
Small egg for body size
Hatch quickly
Laying behaviour:
Very fast to lay eggs in nest (more likely to reject if sees cuckoo)
May re-start host clutch (takes all eggs and forces bird to make a new nest where she can lay in at the right laying time)
Lays eggs same time as host is laying eggs
Cuckoo chick:
Hatched fast for its size
Removes other eggs/ competition
What is indirect coevolution
Insect aposematism:
Warning coloursiation
Often poisonous (eg sting or chemical)
What did Gittleman and Harvey do in 1980
Chick experiment
Predator for chick food/ chick crumbs
Treated so they are either camouflages or stand or but they don’t taste good
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A Breif History Of Life On Earth Lecture320
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History Of Evolution Lecture 18
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Evidence Of Evolution Lecture 215
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Human Evolution Part1 Lecture 418
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Human Evolution Part 2 Lecture 523
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Co Evolution Lecture 828
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Nature Of Biological Variation Lecture 619
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The Origin Of Species Lecture 70
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The Evolution Of Parental Care Lecture 917
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Mating Effort And Sexual Selection Lecture 1023
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Sexual Selection 2 Lecture 1120
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Alternative Reproductive Strategies Lecture 1233
