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Population Change and Evolution

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Presentation on theme: "Population Change and Evolution"— Presentation transcript:

1 Population Change and Evolution

2 Phylogeny The history of the evolution of a group of organisms

3 Adaptation – an inherited trait or set of traits that improve the chances of survival and reproduction of an organism Evolution – the cumulative changes in characteristics of a population in successive generations

4 Theories of Evolution Lamarck
Law of Use and Disuse: organisms can change their body features during their lifetimes to satisfy their needs.

5 Theories of Evolution Lamarck
2. Acquired characteristics are inherited: Those characteristics changed during the lifetime of an individual can be passed on to offspring

6 Ex) Giraffes are able stretch their necks to reach leaves and this trait is passed on to their offspring.

7 Darwin Job was a ‘naturalist’ – recorded and sampled new species
Voyaged on the Beagle to the Galapagos Islands

8 Darwin observed many species
Ex) Finches had adapted to eat blood, use sticks in holes, drill holes

9 Darwin He also noticed curious species:
Iguanas that ate algae from ocean Flightless cormorants

10 Darwin Assumed that all species evolved from a common ancestor, probably from the mainland Ex) armadillo evolved from glyptodont

11 Darwin proposed that evolution occurred by natural selection and published his theory in 1859

12 Another scientist Alfred Wallace had similar ideas

13 Theory of Natural Selection
Overproduction – more offspring produced than survive Struggle for existence – organisms compete within and between species

14 Theory of Natural Selection
3) Variation – exists in any population and the variations are passed on to the next generation (genetic differences)

15 Theory of Natural Selection
4) Survival of the Fittest – surviving organisms are ones better able to compete, survive and reproduce. The others die without leaving offspring (natural selection)

16 Theory of Natural Selection
5) Speciation – over numerous generations, new species arise by accumulation of inherited variations of traits; considered new species when members cannot interbreed with original species.

17 Key Concept Those organisms that live long enough to REPRODUCE will pass their DNA for the ‘desirable’ traits onto their offspring. Those organisms less suited will die before reproducing. The population becomes more fit

18 Giraffes Began with short necks
Those that were BORN with slightly longer necks got more food Could grow stronger to outrun predators, and survived to have babies!

19 How do new traits appear?
Mutation Sexual reproduction produces new combinations


21 Peppered Moths Were white with black spots ( a few were darker)
Industrial revolution – soot on tree trunks

22 Peppered Moths

23 Peppered Moths Within a few years, virtually all the moths were black
Story may be simplified, but many other examples exist Ex. Fish becoming more oblong after net fishing introduced in AB lakes

24 Microevolution Is the changing of an organism (population of organisms) over time without a change in species Eg. Antibiotic resistance

25 Macroevolution Species differences become so great that they are no longer able or no longer interested in interbreeding Geographic isolation often the cause

26 Macroevolution Human evolution – most controversial subject
Evidence especially from Africa/Indonesia

27 Adaptations Driven by natural selection
All help organisms to pass their genes to next generation

28 Structural – structures that improve a species ability to survive and reproduce
Ex. Modification of limbs in mammals Ex. Camouflage

29 Ex) warning colors

30 Physiological – based on chemicals
Ex. pheromones – chemicals that influence the behavior of other organisms (attract mate, alarm) Ex. venom production

31 3. Behavioral – behaviors
Ex. migration, hibernation, phototropism

32 Convergence Very different species may also develop similar adaptations due to similar needs in their environment Eg. Squid and human eye

33 Adaptive Radiation Or divergence
Similar species become quite different due to differing environmental needs

34 Two Versions of Evolution
Gradualism: species gain small changes with time Punctuated Equilibrium: new species born suddenly with better adaptation - This adaptation rapidly becomes the only one in the population


36 Human Origins

37 Evidence For Evolution
Fossil record: organisms that once existed on earth do not exist today (dinosaurs)

38 Evidence For Evolution
Radiocarbon dating – is controversial, but useful for long-scale dating

39 Evidence for Evolution
Embryology– all embryos (from worms to humans) go through very similar stages

40 Evidence for Evolution
Homologous structures have common origins in the embryo (eg. Gill slits, forelimbs of vertebrates) Evidence of a common ancestor

41 Evidence For Evolution
Analogous structure: similar structures, but develop from different embryological structures These organisms do NOT descend from a common ancestor

42 Evidence For Evolution
Eg. Wings of insects, birds and bats

43 Evidence for Evolution Vestigial Structures
Are structures present in organisms that have no present day functions May be ‘left over’ from previous evolutionary stages

44 Evidence for Evolution Ex)
Pelvis and leg bones in whales

45 Evidence for Evolution Ex)
Limb buds and claws in snakes

46 Human Vestigial Structures

47 Evidence for Evolution
Comparative Biochemistry Recent advances in DNA profiling and protein sequencing has allowed us to study the similarities in common molecules

48 Primate No. Of Amino Acids Different From Humans Chimpanzee Identical Gorilla 1 Gibbon 3 Rhesus Monkey 8 Squirrel Monkey 9

49 Evidence for Evolution
Biogeography – study of geographical distribution of plants and animals Theory of Continental Drift – all continents were once joined into one supercontinent called “Pangaea”, then broke apart and continue to move apart today


51 Theories on Origin of Life
‘scientific’ theories based on the “Big Bang” Explosive, outward movement of mass, continuing today Nuclear fusion causes elements to form in stars

52 Origin of Life On earth, a ‘primordial soup’ was formed
Methane, ammonia, water Urey and Miller – famous experiment – caused organic compounds to form when electricity (lightning) introduced to these compounds

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