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NCEA Level 3 Biology Achievement Standard 3.5 ‘Describe processes and patterns of evolution by; Discussing ways in which speciation occurs (sympatric and allopatric )
“Father of Evolution”
From early times, people have tried to explain the origins of human beings and other living things on earth. Cultures, groups of people and individuals have various ideas about how life, earth and humans came about and what it means.
Have the story that Papa, the earth goddess and Rangi the god of the sky, where joined so tightly that no light could come into the world and their children could not escape from between them. Tane, managed to separate them, which allowed light into the world meaning plants could grow and animals survive.
This is a tribe in central Africa. They believed that in the beginning there was only darkness, water and the god Bumba. One day Bumba had a bad stomach ache and vomited up the sun, moon, stars, animals and finally man.
God made the world in 6 days and rested on the seventh. This comes from the old Testament and has been passed on through generations.
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass those advantages to their children
5. Species alive today are descended with modifications from common ancestors
Fossil Record provides evidence that living things have evolved
Fossils show the history of life on earth and how different groups of organisms have changed over time
Australopithecus Homo erectus Homo sapien
Similar animals in different locations were the product of different lines of descent
Geographic distribution- the distribution of related species, especially on isolated islands, provides evidence of how new species have evolved.
Homologous Body Structures
e.g. Wing of bat, human arm, leg of turtle
e.g. Appendix, horse chestnut, dog claw…
Similarities in Embryology
NZ Fur Seal (Arctocephalus forsteri)
from South American mainland
Which one’s which?!!
Punctuated equilibrium: evolutionary model in which there is long periods of little change in the species punctuated by short bursts of rapid change most often associated with speciation. Ancestor is still present.
Gradualism: evolutionary model for the rate of evolution where the accumulation of changes resulting in speciation occurs slowly and steadily over millions of years. Ancestor is extinct.
(Phenotype is the expression of the coding- genotype, that we usually see)
1. Present day species have evolved from ancestral forms.
2. Organisms produce more offspring than survive. The offspring compete for food and other essentials for survival.
3. Offspring produce by sexual reproduction will show variation; some characteristics that are more suited to their environment than others.
4. Those individuals of a species with favourable characteristics will survive longer and produce more offspring to pass their favourable characteristics on. Those with unfavourable characteristics will not survive as long or reproduce as frequently. This is called ‘survival of the fittest’.
5. Successive generations will become modified over time, particularly if their environment is changing. Gradually the species will change sufficiently to be recognised as a new species.
Variation is caused by
This is when a population becomes separated by a geological barrier.
This eventually leads to different species with completely different gene pools.
Canyons and Deserts
Chatham Island Robin
South Island Robin
Once the population has been separated by geological barriers, they become so different they are not able to interbreed if the physical barrier separating them were removed. There can be no exchange between their gene pools because of reproductive isolating mechanisms.
If there are no geological barriers separating populations then the isolating mechanism must be biological. There are two types of biological mechanisms Prezygoticwhich happens before fertilisation and Postzygoticwhich occur after fertilisation.
Describe the Key ideas that underpin the theory of evolution: genetic variation, competition, differential reproductive success (natural selection)
Figure 7.7 Concept of genetic drift. In a large population with random mating, large fluctuations of gene frequency are unlikely. In a small population, however, gene frequency can change dramatically from one generation to the next, if, for example, only the AA individuals participate in mating by chance.
This is a change in the allele frequencies of a population as a result of chance processes. This has a big influence in small populations where chance alone may play a considerable role.
Two examples of these chance events are the genetic bottleneck and similarly the Founders effect.
1. Double disaster: The island fruit flies are now geographically isolated from their mainland relatives, but only a few larvae have survived the harrowing journey to end up colonizing the island.
2. Rare genes survive: These few survivors just by chance carry some genes that are rare in the mainland population. One of these rare genes happens to cause a slight variation in the mating dance. Another causes a slight difference in the shape of male genitalia. This is an example of the founder effect.
3. Gene frequencies drift: These small differences, which are rare on the mainland, drift to fixation in the small population on the island over the course of a few generations (i.e., the entire island population ends up having these genes).
Bottleneck effect- Period in which a population becomes temporarily reduced to very small numbers, as a result of which its genetic diversity becomes reduced.
An example of a bottleneck:Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000—but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
A change in the frequencies of certain alleles in a gene pool over successive generations is called microevolution. This term is often used to refer to small, reversible changes within a species.
Large, irreversible changes in a gene pool, such as those involved in the formation of a new species (speciation) or in adaptive radiation is called macroevolution.
The following agents change the frequency of genes in the gene pool of the population:
This occurs when a certain phenotype is preferred over others. This eventually leads to the decrease in the un-preferred phenotypes.
Mutation is the ultimate source of variation that can change the equilibrium within a population.
This is caused by the immigration and emigration of individuals into a population. This increases and decreased the genes within the population.
Some combinations of alleles are more likely to help survival and reproduction than others. This means that the frequency of these alleles in the population will increase. This is what is meant by the ‘survival of the fittest’.
Directional selection- favours one extreme over the average or the other extremes.
Disruptive selection- favours both extremes over the average.
Dark forms of the British peppered moth (Biston betularia), as well as many other species of moth, became common in the middle of the 19th century near centres of industrial pollution. Soot coated the trunks and branches of trees, and killed lichens. In the photos, a pale form (typica) and a dark form (carbonaria) rest side-by-side on an unpolluted lichen covered trunk in Dorset (above), and a soot-covered trunk near Birmingham. (From HBD Kettlewell, 1956, Heredity 10: 300).