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Chapter 15-Darwin’s theory of Evolution
I. The Puzzle of Life’s Diversity• ___________________-variety of organisms• _________________-change over time• Voyage of the Beagle
– Charles Darwin-sailed____________________(1831) and collected many scientific observations –particularly of interest at the area around S.America and the Galapagos Islands
Biological Diversity
Evolution
H.M.S. Beagle
– Darwin collected ___________ remains-some resembled living organisms and some did not---
indicating species had disappeared.– Observed great diversity and saw so many
organisms were well suited to their environments and various patterns ----leaving him w/ many questions…
Fossilized
– Although the Galapagos Islands were very near S.America,their climates were different than S.America and each other.The _________________ and iguanas varied in predictable ways from island to island/also many observations on variations in birds-eg. Size or shape of beak.
– After returning to England , he began to wonder if the animals on different islands were once members of the same species.
tortoises
II. Ideas that shaped Darwin’s thinking
– Predominate thought was that the earth and inhabitants were only a couple thousand years old.
– __________________ published a detailed hypothesis about the geological forces that have shaped the earth-proposing layers of rocks formed slowly and the physical earth was shaped by a variety of forces..
– _____________________________________ wrote Principles of Geology .---stressed that scientists must explain past events based on processes they can actually observe---eg. By volcanoes that we still observe may we get an idea of how the earth has changed
1795-James Hutton
Charles Lyell in 1800’s
– _________________(1809)-realized organisms change over time but he felt that selective use or disuse of organs caused organisms to acquire or lose traits
• 1) _____________He said all organisms have a tendencies towards perfection ..thus continually acquiring characteristics to improve themselves----Thus he would say birds fly because they long ago tried to and their wings kept developing over the generations to fly.
Lamarck
Perfection
• 2) ________________if something is used it is transformed for that purpose while if it not used,it would eventually disappear
• 3)____________________.---If a giraffe stretched its neck to reach its food,it would pass that trait on…
• 4)Evaluating Lamarck- incorrect in many ways-– He did not know an organism’s
experiences or behavior have no effect on inheritance
USE AND DISUSE
INHERITANCE OF ACQUIRED CHARACTERISTICS
• Population Growth-_____________-reasoned that if the human population continued to grow unchecked,sooner or later there would be insufficient space & food---war,famine and disease work against this
• Darwin realized this applied less to humans than other animals and plants because _______________________________________
Thomas Malthus-1798
People do not reproduce as much young
III. Darwin presents his case
• A. publication
• 1858-Alfred Russel Wallace summarized the thoughts on evolutionary change Darwin had been looking @ for 25 years…This gave Darwin the incentive to publish his work
• 1859—Darwin Published “On the origin of Species…”proposed the mechanism for evolution to be ______________________________________
Natural selection
B. Inherited Variation and Artificial Selection
• Members of each species vary from one another• Some variation heritable-passed on• ______________________selective genetic variation
where nature provides the variation and humans select to breed for this characteristic
Artificial selection
C. Evolution by Natural Selection
– 1) Struggle for existence• Applying Malthus’ principles,He realized high
birth rate and shortage of resources produced _______________________-struggle for existence---faster,etc. avoid being caught
competition
2) Survival of the Fittest
• _____________________=ability of an individual to survive and reproduce
• ___________________=any inherited characteristic that increases an organism’s chance of survival
• Organisms w/ low levels of fitness are unlikely to survive and reproduce
• __________________________________=survival of the fittest….may inherited characteristics of a population
fitness adaptation
Natural selection
3) Descent with Modification
• Over long periods ,natural selection produces organisms that have different structures,establish different niches,or occupy different habitats---each species descends ______________________.
– Implies all living organisms are related to each other
– _____________________________-all species-living and extinct were derived from common ancestors
Modification/changes Common descent
D.Evidence of Evolution
– 1) Fossil Record-record of the history of life on earth-comparing fossils from different layers
– Felt the earth was millions of years old– Since Darwin,people have discovered many
transitional species in fossilized form– Gaps remain—providing some uncertainty
about how some species evolved
2)Geographic Distribution
• With reference to birds he observed,Darwin felt although they varied,they descended with modification from common mainland S.American ancestor
• Animals w/certain similarities between areas developed this way due to similar ecological conditions
3)Homologous Body Structures----structures that have different mature forms but develop from the same
embryonic tissue
• Example:The bones of a bird skeleton more closely resemble homologous bones of certain reptiles than that of bats
• ___________________________-traces of homologous organs….appear to have no function
Vestigial organs
4)Embryological Similarities-many embryos look esp. similar during certain stages of development…
producing homologous structures
E. Summary of Darwin’s Theory• Individuals differ and some can be
___________________________.• Organisms produce more offspring that can survive
and many do not _________________________.• Organisms ______________for limited resources.• Each unique organism has unique advantages and
disadvantages in struggling for existence---Those best suited will reproduce,passing on their traits.
• Species alive today descended with modification from ancestral species…uniting us in a single tree of life
Inherited traits
reproducecompete
Strengths and Weaknesses
• Continues to change as new data and technology develop
• Argument about extinction
• Origin of life
Evolution cont’d-pieces of Chapter 16 & 17
• _____________________=all genes,inc. all the different alleles,that are present in a population
• ______________________of an allele= # times that the allele occurs in a gene pool,compared with the # of times other alleles for the same gene occur.(often a %)
• In genetic terms ,evolution is any change in the relative frequency of alleles in a population.
Gene pool Relative frequency
Sources of genetic Variation-
– 1)mutations– 2)gene shuffling– ----- Natural selection can affect the distribution of
phenotypes in any of the 3 following ways:• 1) Directional selection-Individuals @ one end
of curve have higher fitness than those @ middle or other end-Example-birds w/ large,wide beaks can crack large seeds….If the supply of small seeds decreases,they dominate
• 2) ___________________-individuals near center of curve have higher fitness—example-babies of average weight survive better than very low or high birth weights.
Stabilizing Selection
• 3)______________________________-individuals @ upper and lower end of curve have higher fitness than individuals near middle-example mid-sized seeds become less common and large beaked or small beaked birds both benefit.
Disruptive selection
_________________________________= random change in allele frequency
•
Genetic Drift
___________________________Principle-allele frequencies in a population will be constant unless one
or more factors change it.
• 5 conditions for it(GENETIC EQUILIBRIUM) to hold– 1)genetic equilibrium from generation to
generation– 2)random mating– 3)large pop.– 4)NO emigration or immigration– 5) no mutations or natural selection
Hardy Weinberg
• ___________________= formation of new species
• Due to-• Isolation-reproductive isolation due to
behavorial,geographic or ______________________isolation(reproduce @ different times)
speciation temporal
• ______________________________are scientists who study fossils
Paleontologists
How fossils form:
• sedimentary rock• sometimes an imprint and sometimes a preserved
remains• buried in resin-amber• tar pits
Dating-
– compare w/other sediments and fossils– radioactive dating using half lives-esp. C-14,since its half
life = 5730 years
• Geologic Time scale-see p.421
3 Eras
• Paleozoic,_______________________ and Cenozoic– 1) Paleozoic-diversity of marine life– 2) Mesozoic-increasing dominance of
Dinosaurs,flowering plants appear– 3) Cenozoic-mammals evolved adaptations to allow
them to live in various environments
_________________-are subdivisions of eras
periods
Mesozoic
• Earth’s early atmosphere probably contained H-cyanide,CO2,CO,N,H2S and H2O
• Miller & Urey’s experiments suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds.This was not totally accurate –the experiment-but lead to similar experiments-even producing nitrogenous bases .
• ~ 200-300 million after earth cooled to carry water, cells similar to bacteria developed, beginning w/something similar to a cell membrane
coacervate
Amino acids produced
• Next eukaryotic cells developed by______________________________as a symbiosis formed between prokaryotes….eventually specializing into organelles like_________________
• Margulis supported this in the 1960’s w/the following evidence:– mitochondria and chloroplasts carry DNA similar
to bacterial DNA.– mitochondria and chloroplasts have ribosomes
similar to that of bacteria– mitochondria and chloroplasts reproduce by
binary fission a lot like bacteria
Endosymbiotic Theory
mitochondria
Patterns of Evolution-
• 1)extinction• 2) ___________________________-single species
evolve into several different forms in different ways
Adaptive radiation
3._______________________________-unrelated organisms come to resemble one another
• Convergent evolution
4._____________________________-2 species evolve in response to changes in each other over time
• Coevolution
• 5_____________________-long,stable periods,interrupted by brief periods of more rapid change
In spurts• 6. __________________--opposite of punctuated
equil.---slowly over a long period of time
Punctuated equilibrium
gradualism