Misconception: Evolution is a theory about the origin of life
What can account for the diversity of life? I. Evolution accounts for the diversity of life on Earth Evolution = change over time in inherited characteristics within a population process by which modern organisms have descended from ancient organisms
II. Theories of Evolution A. Scientific theory a well supported testable explanation of natural phenomena ex: theory of gravity, plate techtonics NOT a guess or hunch
B. Jean-Baptiste Lamarck theory of evolution 1809 Lamarck s theory: by selective use or disuse of organs, organisms acquired or lost traits during their lifetime; these traits could then be passed on to their offspring ex: giraffe acquired long neck by stretching for food Problem: Lamarck did not know how traits were inherited
You inherit blue eyes or curly hair from your parents. You acquire athletic skills or the ability to play a musical instrument
C. Charles Darwin contributed more to our understanding of evolution than anyone Over time, natural selection results in changes in inherited traits of a population
III. Ideas that shaped Darwin s thought on evolution A. Made observations, collected evidence in Galapagos Islands off coast of S. America; voyaged on a boat called HMS Beagle in 1831
-observed similar species well suited to the environment they inhabited -traits of similar species varied noticeably among different islands of the Galapagos ex: tortoises and finches -hypothesized that animals adapted to local conditions on islands after their arrival
B. James Hutton and Charles Lyell studied geology in the early 1800 s helped scientists recognize that Earth is many millions of years old; older than anyone believed C. Thomas Malthus and human population growth 1798 if the human population continued to grow unchecked sooner or later there would be insufficient living space and food creating a struggle to survive
D. Farmers and artificial selection -- nature provides the variation humans select those variations they find useful ex: cows and milk production, hogs and muscle, horses and speed
IV. Evolution by natural selection proposed by Darwin in On the Origin of Species, 1859 A. Struggle for existence more offspring are produced than can survive; members of each species compete to obtain food, living space and other necessities of life
B. Survival of the Fittest = Natural Selection individuals with an adaptation that makes them more fit for a certain environment will survive and reproduce at a higher rate
adaptation -- inherited characteristic (trait) that increases an organism s chance of survival Ex: hibernation allows body metabolism to slow so animal can survive long periods with limited food available fitness ability of an individual to survive and reproduce in its specific environment
C. Descent with modification - each living species has descended, with changes, from common ancestor Common descent: -- all species (extant and extinct) were derived from common ancestor -- a single tree of life links all living things
V. Evidence of evolution A. Fossil record - examples of many species that have lived for a time and then became extinct
B. Geographical distribution of living species looking at similar environments on different continents, animals had similar anatomies and behavior because of adaptation
Ex: beaver (N. America) and capybara (S. America) muskrat (N. America) and coypu (S. America) Beaver Beaver Muskrat Muskrat Beaver and Muskrat Coypu Capybara Capybara Coypu and Capybara Coypu
C. Homologous (similar or corresponding) body structures structures that have different mature forms but develop from the same embryonic tissues; strong evidence that all four-limbed vertebrates have descended from a common ancestor
Homologous Body Structures Turtle Alligator Bird Mammal Ancient lobe-finned fish
D. Vestigial organs organs so reduced in size that they are just vestiges (traces) of homologous organs in other species ex: tail bones, appendix (?), tiny leg bones in boas and pythons, wisdom teeth, hip bones in whales
E. Similarities in embryology early stages (embryos) of many vertebrate animals are very similar
F. Components of genetic code and amino acid sequences show evolutionary relationships. a. DNA bases (ATGC) b. Converting glucose to ATP for energy.
Which of these is an example of evolution and why? A year or 2 of drought occurs in which a population of beetles have few plants to eat. The beetles in this population are a little smaller than the preceding generation. 90% of the beetles in a population have a gene for bright color, but 10% have a gene from brown color. Some number of generations later brown beetles comprise 70% of the population.
VI. EVOLUTION OF POPULATIONS (Chapter 16 p. 392-410) A. Population a group of individuals of the same species that interbreed Gene pool all the genes of all the members of a particular population (all alleles) Evolution (in genetic terms) -any change in the relative frequency of alleles in a population
B. Sources of genetic variation within a population 1. Mutations change in the sequence of DNA; if beneficial mutation trait will increase in the population
2. Recombination genes combining in new ways during production of gametes and crossing over (meiosis)
3. Gene flow transfer of genes between populations ex: people moving from one country to another; migration of animals to another population When U.S. soldiers had children in Southeast Asia with Vietnamese women during the Vietnam War, they altered the gene pool frequencies of the Vietnamese population.
VII. Evolution as genetic change A. Evolution by Natural selection: -acts on entire populations not just individual organisms. -never acts directly on genes entire organisms survive to reproduce, or die and do not reproduce.
Single-gene and Polygenic Traits 1. Single-gene: natural selection on single gene traits can lead to changes in allele frequencies and thus to evolution. Ex: polydactyl (6 fingers) versus normal digit number (5 fingers) 2. Polygenic Traits: effects on allele frequencies much more complex
a. directional selection individuals at one end of curve have higher fitness ex. anteaters with long tongue better for capturing ants
b. stabilizing selection individuals near center of curve have higher fitness ex. Human baby weight at birth too small low survival, but too large difficult birth
c. disruptive selection upper and lower ends of curve have higher fitness ex. large and small seeds common birds beaks are large or small
B. Gradualism and Punctuated Equilibrium 1. Gradualism: change that occurs in a species at a slow steady pace 2. Punctuated equilibrium: rapid sudden change in a species ex: light brown and black pocket mice after volcanic eruption in New Mexico
C. Evolution by Genetic Drift a random change in allele frequency Certain individuals may leave more descendants than others, and over time this can cause an allele to become common in the population. Caused by chance, not natural selection.
Genetic Drift:
VIII. Speciation formation of a new species Species group of organisms that breed with each other and produce fertile offspring in the natural environment A. How do new species arise? 1. Reproductive isolation = when members of two populations cannot interbreed and produce fertile offspring.
2. How does reproductive isolation occur? When there are barriers to gene flow. -behavioral isolation courtship rituals or other behaviors are different ex: Eastern meadow lark will not respond to Western meadowlark mating songs Western meadowlark Eastern meadowlark
-geographic isolation population separated by geographic barrier like river changing course, mountains rising ex: one population of squirrels divided into 2 or more smaller populations by formation of Grand Canyon
-temporal isolation populations reproduce at different times can be different seasons or time of day ex: plant species that flower at different times of the year; toad species that live in the same area, but one species mates in early summer and other in late summer.
3. Darwin s finches an example of speciation - descended from a common ancestor from mainland S. America - natural selection shaped beaks as they adapted to different foods on different islands
B. Divergent Evolution process of 2 or more related species becoming more and more dissimilar ex: red fox and kit fox --red fox lives in forest where red color blends with trees; kit fox lives in deserts where its light brown color blends in with sandy environment --similarity in structure indicates a common ancestor, but as they adapted to different environments the appearance of 2 species diverged
C. Convergent Evolution unrelated species become more and more similar as they adapt to same kind of environment ex: cactus growing in American desert resembles cactus which grows in African desert. Both have fleshy stems for storing water and spines to ward off predators. Aloe cactus in Africa Saguro cactus in Arizona
Everyday Evolution: Read this tonight and have all questions answered when you walk in tomorrow.
Everyday Evolution: Let s talk!
Understanding Phylogenies Evolutionary Classification Darwin s ideas about descent with modification have given rise to the study of phylogeny, or evolutionary relationships among organisms.
Understanding a phylogeny is a lot like reading a family tree. The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of that ancestor. As you move from the root to the tips, you are moving forward in time.
When a lineage splits (speciation), it is represented as branching on a phylogeny. When a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages. Speciation to form a new biological species from an existing one
Misconceptions about Humans The phylogeny of living species most closely related to us looks like this: It is important to remember that: Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human.
Is a rose more closely related to tomato or an orchid?
Is the Bonnethead Shark more closely related to the Scoophead Shark of the Winghead Shark?
DOMAIN ARCHAEA DOMAIN EUKARYA DOMAIN BACTERIA Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia