Population Change and Evolution

Phylogeny The history of the evolution of a group of organisms

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

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

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

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

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

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

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

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

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

Another scientist Alfred Wallace had similar ideas

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

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

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)

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.

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

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!

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

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

Peppered Moths

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

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

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

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

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

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

Ex) warning colors

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

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

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

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

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

Human Origins

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

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

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

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

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

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

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

Evidence for Evolution Ex) Pelvis and leg bones in whales

Evidence for Evolution Ex) Limb buds and claws in snakes

Human Vestigial Structures

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

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

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

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

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