Name mechanisms that can be employed by animals to avoid predation?
Social defences. Conspicuous behaviour. Cryptic behaviour of defence.
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Name examples of Social Defences?
Mobbing, aggregating in large groups & herding.
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Name an animal that carries out mobbing?
Black headed gulls.
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What are Social Defences?
Behaviours that species engage in collectively to increase individual survival chances.
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What are the fitness costs of mobbing?
Time and energy expended.
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What are the fitness benefits of mobbing?
Improvement of offspring survival.
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What deems mobbing an appropriate adaptation?
Needs to be better than the alternatives, doesn't need to be perfect.
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Example of where adaptationist theory of mobbing has been tested?
Crows take eggs from gulls. Gulls mob to combat this. Test by laying chicken eggs inside and outside colony. Extent of mobbing should be proportional to level of success of crows hunting.
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What did the study find?
More crows were mobbed with eggs closest to colony. Crows feeding attempts unsuccessful closer to colony. Evidence for mobbing as an adaptation.
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What kind of method is the study with gulls and chicken eggs an example of?
Experimental method.
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What other type of method is there?
Comparitive method.
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What does comparitive methods do?
Test predictions about which species should have evolved specific behavioural adaptations.
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Example of comparitive method being tested in gulls?
Should see gull species with low risk of predation not showing mobbing. This is true - cliff gulls do not do this.
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What is divergent evolution?
When two species evolved from a common ancestor but possess different traits as they lose the need for certain traits. Lose it as part of their evolutionary design.
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Traits are dependent on...
The environment species are in and the selection pressures they are exposed to.
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What are homologous traits?
Shared ancestry traits.
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What is convergent evolution?
Species who share no common ancestor develop similar traits in response to similar selection pressures which lead to similar solutions.
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What are analogous traits?
Similar traits developed in response to selection pressures.
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Example of convergent evolution?
Camera eye in mammals, invertebrates, vertebrates. Look the same, but not homologous. Evolved to do same thing.
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What explanation do scientists usually take?
Easier option.
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What explanation do scientists take for the camera eye?
Convergent evolution. Otherwise if developed from a common ancestor, would have had to been lost at stages then evolved in other groups - very complex. Process most likely most likely to be correct.
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What is parsimony?
Requires fewest changes. Simplest explanation.
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Why does aggregating as a large group work to avoid predation?
Larger the group = less risk of being captured and eaten. Overwhelms predators ability to catch or desire to.
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Is aggregating in a large group for the good of the group or the individual?
Individual.
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Example of aggregating in a large group animal?
Mayflies - syncronise change from aquatic nympth to flying adult. Greater number of mayflies emerging = smaller probability of being eaten. Do this in June.
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Example of animals aggregating in large groups in SPACE rather than time?
Herding in mammals. Reduces chances of being eaten. Equal chance of being eaten when spread out, but when together, this reduces risk.
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How does herding evolve?
Those who group together survive and leave descendants. Those who do not get eaten. Population of herding evolves.
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What is Cryptic behaviour for defence?
E.g. camouflage - colour patterns and behaviour which reduce predation.
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Who takes part in cryptic behaviour for defence?
Solitary creatures.
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Example of cryptic behaviour for defence?
Revolution - blackening of trees - molanic moth faired better (black).
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Whats an important consideration of cryptic behaviour for defence?
Appropriate resting space. Need to pick somewhere where animal will blend in or this is ineffective.
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Name another defence mechanism?
Conspicuous behaviour.
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Example of animal that does this?
Monarch butterfly. Eat toxic milkweed as caterpillar.
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Example of another animal that does this?
Tephritid fly. Mimics predator (spider).
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Name another defence mechanism?
Stotting.
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Who displays this behaviour?
Gazelles.
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Explanations for stotting?
Alarm call. Social Cohesion (attract gazelles to join). Confusion effect (if whole herd are doing it). Signal of unprofitability (signal to show they have enough energy to do this, poor prey as they can outrun them - deterrant).
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