evolution
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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. - PowerPoint PPT PresentationTRANSCRIPT
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