B3 Topic Two - Behaviour and Evolution

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Innate and Learned Behaviour

Behaviour is an organisms respone to changes in its environment. Normally in order to survive. Genes and environment affect this. Most behaviour is a mix of inherited/learned.

Inherited = innate behaviour. When one can respond to a stimulus correctly immediately. e.g. newborn mammals suckle from mothers.

Can be simple reflex or compicated behaviour like courtship rituals.

Simplex reflex(automatic) : e.g. sneeze, blink to protect from dangerous stimuli

Complex reflex(automatic): Earthworms are negative phototaxis. Sea anemones wave tentacles more when sense chemicals emitted by their prey.

Learned behaviour lets animals respond to changing conditions. Learn from experiences.

Habituation: Animals learn to ignore stimuli that arent benificial/harmful, so can spend time and energy more effeciently. e.g. crows learn to ignore scarecrows.

Mixture: Imprinting - has instinct to follow first moving object, if parent: helps to survive as provides shleter/food: learns to recognise parents and instinctively follows them

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Conditioning - Learned behaviour

Classical Conitioning - when animal learns passively to associate a neutral stimulus with an important one. The link is automatic but reiniforced by repitition.

Ivan Pavlov - studied dog behaviour. Dogs salivate when they see/smell food. Began to ring bell before giving food. Dogs soon began to salivate when bell rang.

Operant Conditioning or 'trial and error learning' - when animal learns actively, to associate an action with a reward/punishment. Humans - kids are rewarded or punished for behaviours.

Burrhus Skinner - trained rats and pigeons to gain food reward using Skinner box (special cage). Choice of buttons - when right one pressed, animal rewarded with food. Pigeons and rats used trial and error system to learn which button to press to get reward.

We use both types of conditioning to train animals. Usually operant - give rewards when it does what you want etc. Physical e.g. choke chains, or verbal punishments. Punishment not recommended though - just as good as verbal but more stressful. Operant - police train sniffer dogs, and police horses to only respond to riders, guide dogs to wait at roadside.

Classical conitioning in combo with operant when reward cant be given at the time the act is done. E.g. dolphin trainers whistle when dolphin jumps, then the dolphin associates the whistle with getting fish.

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Social Behaviour and Communication

Animals in a group communicate to: keep group together, warn of predators, communicate mood to prevent unnecessary fighting, babies to tell parents their needs, coordinate attacks.

Communication by sound, e.g. whales and dolphins use low frequency sound for long distances. Bird calls declare territory, attract mates and warn of predators

Chemicals - pheromones released to tell location. Many use chemical scents to mark territory. Other chemicals are sexual attractants - moths can detect females from km away

Visual signals: honey bess move in a 'wagge dance' when they return to the hive to tell where they found food. Mammals through gestures and body posture e.g. to threaten/intimidate, chimps stare or raise their arm. To admit defeat, dogs roll in back to show submission. Courtship behaviours - dances, gifts, fancy nest building. Facial expressions - chimps open mouths wide to show fear.

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Animal Behaviour Studies

Ethologists study animal behaviour.

Tinbergen studied innate behaviour in herring gulls. Newborn gull chicks know how to pick at parents beak for food - have a red spot on beak. Showed chicks cardboard gull heads with different colour spots on beaks. Counted no of times chicks pecked on different colours. Noticed red more often - concluded that it is an instict to peck at the red to help find food.

Lorenz studied how baby geese/other birds imprint. Took two groups of geese eggs. Group 1 first saw mother. 2nd group saw Lorenz first - treated him the same - shows birds form attachment to first moving object they see (imprint) which helps them recognise mother.

Fossey + Goodall studied social behaviour in apes. Fossey studied African mountain gorillas, Goodall studied Tanzanian chimps. Studied in natural habitats so could see real behaviour. Gorillas and apes are social animals that live in groups. F+G saw they worked together to find food - more efficient. Protect each other - efficient. Males had social rank which prevented fights (waste energy) as knew their place. Groomed each other - kept clean, reinforced social bonds, helping keep the group together. Also strengthed bonds by showing affection - hugging!!

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Investigating Animal Behaviour

Choice chambers investigate how animals respond to environmental conditions. Different conditions in each section e.g. dark, wet. See which is closest to natural habitat. However, control other conditions for fairness e.g. same temp and size 

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Mating Behaviour

1. Male birds, whales, frogs perform song or call to attract females

2. Female insects use pheromones:sexual attractants e.g. male moth smell from km away.

3. Fight displays e.g. deer to indicate strength

4. Courtship displays. Posturing, dancing, showing bright colour parts. Species specific. Link - how good display + fertility. Mandrill: bright face+bum testosterone level.

Women have more input in child rearing, so choose male specifically, not too closely related, to ensure he, (so kids will be) strong and fertile, kids have best chance of survival, so males have to show worthy of selection - job is to mate with as many as possible.

Monogamy - birds:swan, penguin, parrot. Mammals:gibbons, prairie voles rare elsewhere

Most species male:no part in child rearing:goes off and mates with others during season.

Some birds e.g. mate with one female each season but different each year

Some mammals e.g. lion have a group of ladies he stays with - harem

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Parenting Behaviour

Some animals look after young, some leave once birthed/hatched. Care involves:

Protection: one parent staying to keep young together/fend off predators. Or construction of elaborate nests. e.g. weaver bird makes ball nest, predators hardly notice the nest.

Feeding: usually involves on parent staying, other gets food - both involved.

Teaching learned behaviours/skills - young mostly learn by imitating parents apart from humans who use mostly language to teach. However hard tasks - oystercatchers open mussels - months for the young to learn to do well. Humans - eating with cutlery, dressing.

Looking after young is risky for mum - shared food, time spent, less chance of escaping predators if protecting young. However, parental care increase young survival. Also, less risky for mother than being pregant - more difficult to escape, puts strain on body. If they give parental care, they can have a less developed baby - shorter pregnancy - less time at risk - only mammals though.

It is the survival of animals genes that it is important, not the animal itself.

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Plant Communication and Co-evolution

Plants can release chemicals to attract insects and warn other plants: Attract pollinators, which carry the pollen. Attract insect predators - when an insect pest is eating them, plant release chemicals - attract a predator insect to feed on the pest, kills it.

Some plants have leaves that release chemcials if being eaten by insects. Another plant/leaf on the same plant detects it, makes chemicals that make its leaves harded to digest.

Co-evolution - when two organisms evolve in response to each other

Example A: Advantage for insect of its the only insect that can get nectar from a type of flower. Advantage for plant if only one type of insect can get its nectar: more likely to visit same type of flowers + pollinate. Some plants + insect pollinators have co evolved. Orchids - deep nectar stors - moth type that has a really long mouth to reach.

Example B: Advantage for plant if can make nasty chemicals so most insects dont eat it. Advantage for insect if it can eat what others cant- some insetcs have evolved to eat poisonous plants - caterpillars of the cinnabar moth eat ragwort (poison to others).

Companion planting - two species together, one is crop, one helps the crop grow - attracts insect predators/sends away pests e.g. cabbage and marigold

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Fossil Evidence for Human Evolution

Fossils give us clues about our human ancestors - humans+ancestors = hominids

Ardi: a fossil homind, 4.4 mil yrs old, Ardipithecus ramidis.  Found Ethiopia.

- Feet structure (ape big toe for branch grasping) - climbed trees

- Long arms short legs - ape.      - Brain size - chimp   

- Hand+leg structure - didnt use hands to walk, walked upright - human

Lucy: fossil hominid, 3.2 mil yrs old, Australopithecus afarensis, ethiopia

- Larger brain than Ardi, still chimp      - Arched feet - better for walking than climbing

- Arms+legs - what youd expect middle of human/ape 

- leg + feet structure - walked upright more efficiently than Ardi

Turkana boy, **** erectus, 1.6 mil, Kenya by Richard Leakeys team - found many fossil

-Short arms long legs -human. -Brain size similar human -Feet+ leg- v. efficient at walking

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Further evidence for Human Evolution

The development of stone tools - shows brains getting larger as tools more complex:

Homo habilis (2.5-1.5 mil yrs ago) - simple stone tools called pebble tools by hitting rocks together to make sharp flakes - scrape meat from bones etc.

Homo Erectus (2- 0.3 mil yrs ago) - sculpted rock into shape to make more complex tools - simple axes. hunt dig chop scrape meat.

Homo neanderthalis(300,00-25,000) - more complex. Flint tools pointed tools wood spears.

Homo sapiens(200,000-present) - flint tools widely used. Pointed tools: arrowheads, fish hooks, buttons and needles appeared around 50,000 years ago.

when an ancient tool is fined, scientists can work out how old it is by:

Using stratigraphy - study of rock layers - but rock layers may so not always accurate

Dating any fossils found with the stone tools.

Carbon-14 dating to date any material found with it made of carbon e.g. wood handle

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Mitochondrial DNA as evidence for Human Evolution

Small peice of dna inside the mitochondria, seperate from dna in nucleus. Inherited from mothr, so is not mixed dna.

More different 2 mitochondrial dna samples are, further back they shared a common ancestor. Studies show everyone has similar mitochondrial dna - everyone descended from one woman - Mitochondrial/African Eve. Some bits of mitochondiral dna vary from person to person as it has high mutation rate: by analysing these mutations, scientists have worked out Eve was african, 200,000 years ago - shows **** sapiens evolved in africa and then spread.

Nuclear dna (dna in nucleus) also shows evolution and migration, but mitochondrial dna is more useful for this because there are lots of mitochondria in a cell - lots of copies, also and linked to that it is less likely to degrade over time.

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Mitochondrial DNA as evidence for Human Evolution

Small peice of dna inside the mitochondria, seperate from dna in nucleus. Inherited from mothr, so is not mixed dna.

More different 2 mitochondrial dna samples are, further back they shared a common ancestor

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Climate change and human behaviour

As humans MIGRATED out of africa, they CHANGED BEHAVIOUR so as to survive in new environment. First moved to coastal areas of the Near East and Asia:

- Had to change diet to seafood - so had to invent new tools to get e.g. shellfish out of shell

Then to hotter lands - Australia: - Diet - fruit on trees in rainforest - new tools - long sticks to knock down fruit

Then to the cold climate of Europe: - Diet -new plants/animals. Large animals - new tools for preparing them to eat, new hunting techniques - groups. Build more shelters - cold. warmer clothes - animal skins.

Have also changed behaviour to survive ice age: long periods of very cold climate: - Build more shelters/use caves   - Discovered fire     - Warm clothes - skin, fur - Hunting for animals increased     - More tools needed for hunt, skinning, building - Cooperation+communication needed to survive - more complex language

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A useful set of revision cards for the Edexcel specification section on behaviour and evolution which could also be useful for students studying these topics in other specifications.  Team these with a set of flashcards and a good set of notes for a complete set of resources.


 A useful set of revision cards for the Edexcel specification section on behaviour and evolution which could also be useful for students studying these topics in other specifications.  Team these with a set of flashcards and a good set of notes for a complete set of resources.

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