Evolution

Year 10 Science

Evolution

Life appeared on earth over 3000 million years ago.

As time passed life forms changed and developed into the organisms of today.

This change is known as evolution.

Evolution definition

Evolution is the change in organisms over time.

Variation

Of all the variations that exist in animals some will help them to survive in their environment.

Adaptations

Nature ‘selects’ the variations with survival value.

These variations with survival value are called adaptations

Adaptations

“Any specific inherited structural or behavioural characteristics that enhance an organisms ability to survive and reproduce in a particular environment”

Adaptations

Adaptations can be classified as; structural - where the adaptation is

physical Behavioural - where the adaptation

controls the way they act

Adaptations

Behavioural Structural

List all the adaptations of a;

Polar bear

Lion

Camel

Rabbit

Variation

Variations are the result of the random assortment of chromosomes during meiosis, and the combination of gametes (sex cells) during fertilisation.

Further genetic variation occurs as a result of mutations.

Survival

The organisms best adapted to their environment are the most likely to produce offspring and pass on these favourable characteristics.

The theory of evolution

This gradual development of different species from a common ancestor is called evolution.

The word ‘evolution’ is derived from the Latin evolutus, meaning unrolled.

Alternatives to evolution

Early theories of evolution

George Buffon (1707-88) suggested that species could change.

Erasmus Darwin (1731-1802) suggested one species could change into another.

Jean Baptiste Lamarck (1744-1829) thought that characteristics acquired during a creatures lifetime then could be passed on.

Early theories of evolution

Charles Darwin (1809-82) was convinced that species developed from a common ancestor.

Darwin was prompted into publishing his work after Alfred Russel Wallace (1823-1913) developed an identical theory.

Darwin’s theories

Darwin and Wallace were the co-developers of the theory of evolution by natural selection.

Darwin’s theory1. A species produces more offspring than

can survive.2. There is variations among the offspring.3. Those best suited to their environment will

survive and reproduce.4. Favourable variations are passed down to

the offspring increasing their chances of survival.

Natural Selection

Natural selection is sometimes called survival of the fittest.

The best adapted individuals will survive long enough to reproduce and pass on their successful characteristics to the next generation.

Those individuals that do not adapt to their environment usually die out.

Artificial Selection

This is the process by which humans select those characteristics that are valued.

Only the individuals with the favourable characteristics are allowed to reproduce.

Selection of peppered moths

http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/natural-selection-game/the-evolution-experience.html

Peppered Mothshttp://www.techapps.net/interactives/pepperMoths.swf

1. Draw a data table similar to the one shown below where data is recorded for moths after 5 minutes of running the simulation.

2. Explain how the color of the moths increases or decreases their chances of survival.

3. Explain the concept of "natural selection" using your moths as an example.

4. What would happen if there were no predators in the forest. Would the colors of the moths change over time? Defend your answer.

Percent Dark Moths Percent Light Moths

Light Forest

Dark Forest

Speciation

A species is defined as a group of organisms that normally interbreed in nature to produce fertile offspring.

The formation of a new species is called speciation

The evolution experience

http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/natural-selection-game/the-evolution-experience.html

Geographic isolation

The first step in speciation is geographic isolation.

Different populations change through natural selection and mutations.

Subspecies appear different but are still capable of interbreeding.

Reproductive isolation

Reproductive factors that may cause speciation are:Mates are not recognisedDifferences in mating seasonsChromosomal changes

Types of evolution

Divergent evolution

the idea that many new forms can evolve from a single ancestor.

The idea is that new environments are inhabited, causing the evolution of new species.

Types of evolution

Divergent evolution - Marsupials

Types of evolution

Convergent evolution Occurs when organisms evolve and

end up having similar adaptations. This is due to:• living in similar environments• having similar habitats and lifestyles.

Types of evolution

Convergent evolution

Types of evolution

Parallel evolution, Occurs where related species evolve

similar features while separated from each other.

The result is organisms that look alike and have common ancestry, but are found in different locations.

Types of evolution

Parallel evolution - Monkeys

Evidence for evolution

Evidence for evolution comes from palaeontology, the study of fossils

Fossils are the preserved evidence of past life usually found in sedimentary rocks.

The fossil record allows us to trace major events in the history of life on Earth.

Fossils

Fossils may be the:• actual remains of organisms (e.g. mammoths

frozen in ice, insects trapped in a type of sap called amber)

• hard parts of organisms (e.g. shells, teeth and bones)

• impressions of organisms (e.g. hollowed casts, moulds where substances have replaced the organism) or

• evidence of the presence of organisms (e.g. footprints).

The appearance of life

In 1953, S. Miller and H. Urey passed electric sparks into a gas mixture that was thought to be similar to the early atmosphere of the Earth. Organic molecules were produced.

The history of the world

Transitional forms

For major groups of organisms, transitional forms have been found in their evolutionary pathway.

Modern vertebrates appear to have evolved first as jawless fish, then bony fish, then amphibians, reptiles, birds and finally mammals.

Transitional forms provide the links between them all, including the air-breathing crossopterygian fish, and the bird-like reptile, Archaeopteryx.

Other evidence for evolution

Anatomical studies Comparisons of the anatomy of

various organisms provide indirect evidence of their evolution from common ancestors.

These fundamentally similar structures are called homologous structures.

The basic pentadactyl limb (a limb with five digits)

Other evidence for evolution

Embryonic development Embryos of different life forms are

very similar in the early stages of development.

Other evidence for evolution

Body chemistry Certain proteins are commonly in a

large number of organisms.

Large differences in amino acids correspond to large differences in appearance and smaller differences are found in animals that look similar. Therefore proteins can be used to predict evolutionary relationships.

Other evidence for evolution

The distribution of plants and animals Biogeography is the study of the

distribution of plants and animals.

Genetic evidence

The basic genetic code is the same in all living organisms.

Eg – the genetic make-up of the chimpanzee is 98.5% identical to a human.

This supports the idea that all living things evolved from common ancestors.

Human Evolution

KINGDOM - AnimalPHYLUM - ChordataSUB PHYLUM - VertebrataCLASS - MammaliaORDER - PrimateFAMILY - HominidaeGENUS - HomoSPECIES - sapiens

Human evolution

PrimatesHumans belong to the order Primates and have many of the features of the primate group. Primates (including us) have:

• forward-facing eyes that allow binocular vision• pentadactyl digits (five fingers/toes on each limb)• four upper and four lower incisor teeth• opposable thumbs (for grasping things)• nails (not claws) on the fingers and toes• large brains for their body size• a flexible skeleton, with arms that rotate in the

shoulder socket to allow them to reach behind their body (great for swinging in trees!).

Human evolution

Humans are unusual, as we also:• walk upright (are bipedal)• have fewer and smaller teeth than the apes• have a flattened face• have a very large skull capacity, and large

brain, about three times larger than that of apes

• make and use tools• use various verbal and visual languages to

communicate• are self-aware.

Possible evolutionary tree for primates

Hominoids

The hominoids include the lesser apes (gibbons), great apes (gorillas, chimpanzees and orang-utans) and humans.

The earliest humans almost certainly arose from the same common ancestor that produced the other hominoids.

Although they have similar ancestors, apes and humans are very distantly related, taking different evolutionary pathways millions of years ago.

Human family tree

Australopithecus (southern ape)

Lived in Africa 4-2 MYA

Fruit eating beings who developed co-operative behaviour and family structures.

There were several species A. afarences A. africanus A. boisei A. robustus

Homo habilis (handy man)

Lived in the African savannas 2-1.5 MYA.

Made the first stone tools.

Were scavengers not hunters.

Worked together in groups.

Homo erectus (upright man)

Lived 1.8 MYA and spread from Africa to Eurasia.

Developed a complex social structure and wore clothes.

Harnessed fire and communicated through sign language.

Homo neanderthalensis (Neanderthal man)

Appeared 35,000-100,000 years ago.

These cave dwellers used tools and buried their dead.

Subsided on meat and could speak

Homo sapiens (intelligent man)

Evolved 150,000 in Africa and spread world wide establishing settlements.

Had a complex language, developed art, agriculture and abstract thought.

Humans during stages of evolution

Human evolution

Australopithecus Homo habilis Homo erectus Homo neanderthalensis Homo sapiens

Cultural evolution

Cultural evolution - The accumulation of learning and knowledge passed on from generation to generation.

Humans have also changed in non-physical ways.

We have learnt reasoning, speech, writing and a sense of right and wrong.

Evolution in the future