1. IB Biology-Chapter 5-Evolution and Biodiversity

2. Evidence for Evolution
Darwin and Wallace
@ age 22 Darwin sailed the HMS Beagle (1831)-for 5 years
Alfred Russel Wallace independently developed a similar theory
They presented ideas to Linnaean Society (1858)

3. Process of_________________________________
Heritable implies it’s not necessarily fast
Cumulative implies that 1 change is not usually enough to have a major impact on species
Process of cumulative change in the heritable characteristics of a population

4. Population-tells us it does not just affect 1 individual
Speciation can arise if enough changes occur in a population- because the members of the new population do not have enough from pre-existing population to interbreed-rarely observable during human lifetime
All life on earth unified by common origins
Neo-Darwinism (modern synthesis)-how DNA shows evidence for evolution by natural selection more than any evidence thus far

5. The fossil record and evolution
It is impossible to go back in time-thousands or millions of years ago and come up w/all the possible fossil evidence
Fossils-petrified remains/traces of animals and plants-been collected for ~ 2 centuries
Fossil record=accumulation of evidence from fossils

6. Convincing evidence compiled by paleontologists:
Life that existed > 500 mya greatly different than today
While earth has had oceans most of its existence, fish fossils have only been found in rocks 500 my old or younger (< 15% of the 3.5 billion y existence of life on earth
Although most top predators today are mammal-e.g. Bears, orcas, big cats, and wolves, none were time of dinosaurs or before
Apart from organisms such as certain sharks, cockroaches, and ferns, most organisms present today have no similar form in fossil record
Life on earth appears to constantly be changing, but most changes are over 100’s, thousands, or millions of years

7. Aging fossils By examining the differences in ratios of isotopes
E.g. A fossil of higher amt C-14 is younger than one w/less C-14
C-14(14C)-slowly loses radioactivity to become N Decay=process of radioactive parent isotope changing into stable daughter isotope
Half-life-speed by which this decay happens-_________________
time it takes ½ parent isotope to decay into stable daughter isotope

8. 14C half-life=__________-so, when an animal dies, their bones will have lost ½ their14C after 5730 yrs./after 11,460 yrs. ½ of that (25% original) will be decayed
So-looking ratio of radioactive C-14 to stable N-14, you can determine age of fossil—If there is 12.5 of radioactive isotope and of stable,3 half-lives have passed (17,190 yrs.)
After a certain # of half-lives, there are so few 14C atoms that it’s difficult to determine age accurately
5730 yrs

10. There are other isotopes w/longer half-lives, such as K-40
There are other isotopes w/longer half-lives, such as K-40. When minerals in rocks crystalize from magma, they contain a % K-40-Once they have hardened and crystallized, no more K-40 can be Added-However the # reduces as the isotope decays into more stable forms-used to determine age of rocks having formed from magma or lava between 100,000 yrs-4.6 billion years ago

12. Artificial selection and evolution
Fossil record far from complete, but we have a good record of changes in heritable characteristics from science of breeding domesticated animals
After practicing selective breeding for dozens and sometimes hundreds of generations, farmers and breeders realized that certain varieties of animals now had unique combinations of characteristics that did not exist before-evolution as a result of an accumulation of sm changes over time-_______________
∴ this is artificial selection = people choose the traits to be reproduced—not a driving force in evolution of natural ecosystems
by human choice

14. Evolution of homologous structures by adaptive radiation
__________________________-similar in form but found in SEEMINGLY different species-as evidence of evolution
E.g.- pentadactyl limbs in humans, bats and whales-shape and # bones may vary, general format the same, even though they may have different functions
Darwin explained homologous structures were evidence of common ancestors
Whales should be able to swim fine whether or not they have 5 phalanges-indicating more the reasoning behind common ancestry
Homologous anatomical structures

17. Species divergence speciation
________________-process of an evolving population changing significantly enough so that the production of offspring w/ original population becomes impossible—i.e. 2 pop’s of a species have diverged(separated) and new species evolves from old one-both species continuing on separate ways
speciation

18. Adaptive radiation
Occurs when many similar but distinct species evolve relatively rapidly from a single or sm # species
Happens when variations w/in a population allow certain members to exploit a slightly different niche in a more successful way
By natural selection and the presence of some kind of barrier (such as water or a mt range), a new species can evolve

19. E.g.-primates of Madagascar and Comoro Islands-off SE coast of Africa.MYA, w/o competition from other primates, lemurs were prolific- large # offspring meant a greater chance for diversity
Among the range of variation in Lemur species-some are better adapted to trees and some to the ground-and some to the desert
Some are nocturnal while most are diurnal
There are so many species due to _______________
Not a single species found anywhere else in world, yet fossils have been found on coast of Africa, Europe, and Asia
It is believed lemurs were not successful in competing w/apes and monkeys-since as soon as traces of the other primates started to become prevalent in the fossil record, the lemur –like organisms became rare
adaptive radiation

20. This would explain why continents and islands tend to have either prosimians or anthropoids-but not both
Dozens of species have become extinct recently-esp. because of human anthropoids

21. Darwin’s finches of Galapagos Islands and Hawaiian Honeycreepers

22. Continuous variation and the concept of gradual divergence
In the diagram (phylogenetic tree) above-species A, B, C, D came from a common ancestor-If any 2 tried to mate-they would not produce fertile offspring
The above picture show how one species can have various splits over time-creating more diversity among species
Sometimes branches on phylogenetic tree are so far apart that the species no longer physically resemble each other (eg-Darwin’s finches)-yet many species can spread over a wide geographical area

23. Eg-NOS-p.225 saltmarsh grass—species that has a wide geographical distribution, there can be measureable differences in DNA-because the climate and soil are different in different locations-∴ the pop’s adapt to the conditions available to them-and some versions of genes will be selected for and others will be selected against, so that the pop’s are best adapted to their areas=___________(any phenomena which alters the behavior and fitness of living organisms within a given environment)
If this continues to produce genetic differences over a long enough time, it is not difficult to imagine a which the differences are so separated that they become different species
There comes a tipping pt beyond which differences outweigh similarities and can no longer freely reproduce
selective pressure

24. Transient morphism---w/in a pop-there is often more than 1 common form
Polymorphisms-different versions of a species - (different shapes-) can be result of mutation
E.g.-Bison betularia-peppered moth-can have a peppered(grey) form or a melanic(black) form-melanic is a rare mutation that usually affects <1% of a population
Grey form well camouflaged against light-colored surfaces, such as tree branches covered w/lichens
The melanin(bulk) form is easily preyed upon by birds against light lichens
From ~ 1860 a phenomenon was underway that cont’d for more than a century- Melanic form(carbonaria) was increasing in #’s
Lichens sensitive to air pollution-industrial revolution producing SO2, which kill lichens-also a lot of blk soot
Result was lichen –free, soot –darkened branches-more difficult for light – colored moths to survive predation
Near industrial areas, the carbonaria were % of all the peppered moths
@ present carbonaria rarely go above 30%-often 0%(improvement in air quality-UK Clean Air Act of 1956)
Transient polymorphisms—changes from light –to dark-and back to light