how did the variety of living things on earth come about?
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How did the variety of Living things on earth come about?
Many hypothesis:1. Religious view that the earth was created along with all the living things in it at most 10,000 years old
2. Georges Buffon 1700s studied fossils and suggested that they would be older than the thousands of years as thought.
3. Lamarck's hypothesis of Use and Disuse or Inheritance of acquired characters
Lamarck's theory has been completely rejected but he is still well respected in the scientific circles why?
An organism can use a body part which then develops. Any part not used much may wither away. The parent will pass on this characteristics to the offspring. Ex. Giraffe stretched it's neck which became long and its offspring was born with a long neck
Weismann disproved this theory when he cut off the tails of rats before they mated but always had babies with tails
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• Well educated• Son of a well known doctor• Dropped out of medical school. Why?• Went back to college to study theology and become a country pastor• But his heart was not in it and .....
Got the opportunity to be a ship's captain's companion as it made a exploratory voyage to chart the new lands that were discovered
Who was Charles Darwin?
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Malthus
Henslow
Who were the most influencing people in Darwin's Life
Botanist and life long friend introduced him to the ship's captain Fitzroy of the Beagle
Captain Fitzroy
Sailed with him on the Beagle
Economist who suggested that the human would soon exhaust earth's bounties and die
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Lyell
Emma
Who were the most influencing people in Darwin's Life
Geologist and life long friend who studied rock formations and suggested that the earth was older than thought
His wife who was his life long friend, supporter , proof reader and editor of all his books.
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What did Darwin see on the Voyage on the Beagle?
His Quote: "Blind man being given sight"
His discovery is often quoted as being even greater than or equal to Galileo and Copernicus
In Brazil
Argentina like armadillos today
modern armadillo
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What did Darwin see on the Galapagos Islands?
Giant tortoise
Different types of finches in different islands and different from mainland of S America
Which is a marine iguana and which one is the land iguana?
Generic Tortoise
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Darwin did not publish this work for 20 years
Was afraid because it went against the religious beliefs of the time
Meanwhile Alfred Russel Wallace on a similar voyage, came to the same conclusion and consulted Darwin and encouraged him to publish
Both published together in 1858
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What was Darwin's evidence for his theory?1. Looked at nature animals and plants on the Galapagos and compared to the mainland organisms.
2. Looked at similarities between different organisms specially humans and apes
3. Looked at how farmers and breeders changed animal and plant characteristics by artificial selection
4. Looked at fossils. Saw a gradual change in the structures of organisms
Darwin's/WallaceTheory of Natural Selection:
1. There is always variation in populations (every individual is slightly different from others because of the genes and mutations they have inherited) Ex.
2. Many more young are born than that will survive to become reproducing adults. Ex
3. The variations that are favorable for a particular environment will allow those individuals to survive and grow to adulthood. Ex
4. Those that survive and reproduce will produce offspring that will inherit those characteristics (they are fit) Ex.
5. Over long periods of time population change and new species form Ex.
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What is speciation?
http://www.pbs.org/wgbh/evolution/darwin/origin/
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Peppered Moth Simulation game
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a) Acclimation/habituation Ex. you can survive the winter with warm clothes, plants growing towards light have a S shape stem
b) Heritable characteristics that individuals are born with Ex. Some vines will climb any hard surface to reach the top, polar bears have thicker fur than camels that allow them to survive colder weather.
Which one does natural selection act on?
B.
1. Mutations
2.
What is adaptation?
Individuals do not evolve populations do
How?
Natural selection acts on gene expression. A population have a "gene pool" (all the genes in the population) Ex. what is a gene pool of a population of giraffes? Humans? Oak trees?
Individuals have different combinations of genes.
Variation results from individuals inheriting different gene combinations that result in their
a) Being able to survive better in the environment offspring will inherit these traits and subsequent generations will show the change (population will change)
b) Not being able to survive no survival of offspring traits dies out
c) Have no effect on their survival rate
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Mechanism of Natural Selection
Directional Selection:A change in gene combination due to a specific environmental condition
Ex. Scarcity of grass for the giraffes, antibiotic resistance in bacteria, pesticide resistance
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How are species formed? Chap 17.717.9 Species definition: A group of individuals that are capable of interbreeding a producing fertile young.
Applies to sexually reproducing species i.e. Any structural, functional or behavioral trait that favors reproductive isolation (as a result of mutation) that will separate two populations.
Mechanical isolation cannot mate/pollinate due to physical incompatibilities (body part differences) Ex. Two sage species are pollinated by pollinators that are different in size
Behavioral Isolation Courtship displays among birds are specific to different species. A female is hardwired to respond only to the courtship of her own species
Calliope Hummingbird
Temporal Isolation Reproduce at different time Ex. Cicadas with 17 year cycles and those with 13 year cycles
Ecological Isolation Live in different places Ex. Siberian tiger and the Indian tiger
Gamete Mortality What if all of the above barriers are broken and two species do mate ... the sperm will not be able to fertilize the egg. Ex. If the pollen of one species lands on a different flower, fertilization will not occur. This is how many closely resembling plants and animals occupy the same ecosystem but never cross breed.
Hybrid inviability If mating happens anyway because all the of the above barriers are overcome, the hybrid embryo does not develop or dies early due to chromosome and gene incompatibility
Hybrid sterility Sometimes species are so closely related that they could break all of the above and mate but ... offspring will be sterile Ex. Mule
Spatuletail Hummingbird
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Three Models of speciation depending on how the populations became isolated
Allopatric speciation Physcial barrier between two populations , prevents their interbreeding, population accumulate separate mutations and eventually become so different that they will not interbreed even when they do meet later. Ex. Earthquake, change of a rivers course, advancing glaciers, movement of the tectonic plates.
Finches and other animal and plants of Galapagos,
Sympatric speciation two groups living in the SAME geographic area, fail to interbreed and eventually become two different populations of species. Also as a result of polyploidy (only in plants) EX, cichlid population in a lake in Cameroon
Red monkey flower pollinated by hummingbirds and pink monkey flower pollinated by bees.
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Parapatric Speciation Population are Separated geographically but not completely. There are some areas of overlap but when mating happens among these population the offspring may be viable but will characteristic of a hybrid type and not as fit. Increased species diversity. Ex. Tennessee cave Salamander, Rock Lizards, Some species of conifers, etc.
Tenessee Cave Salamander
Grass capable of growing in metal contaminated soil so has changed its flowering times and cannot reproduce with its parent types.
Review
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16.5 not on test
16.6 About Mutations only know what mutations are and they are acted on by nature and the best one for that environment is selected NATURAL SELECTION
16.7 16.8 Mechanism of Selection
16.9 Read to understand but no specific questions on test
16.10 What is genetic drift?
random changes in gene frequencies due to chance that results in a small population rebuilding the population or start a new one
1. Bottleneck: A drastic reduction in population due to severe pressure or calamity, ex. disease, hunting, habitat loss
Ex. Cheeta, elephant seals
2. Founder effect: When a few individuals found a new population by chance. Ex plants and animals on Galapagos. Amish in US
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