EVOLUTION

EVOLUTION BENCHMARKS 1.DESCRIBE WHAT BIOLOGISTS CONSIDER TO BE EVIDENCE FOR HUMAN EVOLUTIONARY RELATIONSHIPS TO SELECTED ANIMAL GROUPS. 2. EXPLAIN HOW A NEW SPECIES OR VARIETY MAY ORIGINATE THROUGH THE PROCESS OF NATURAL SELECTION. 3. EXPLAIN HOW NEW TRAITS MAY ARISE IN INDIVIDUALS THROUGH CHANGES IN THEIR DNA.

1.JEAN LAMARCK- believed species could change their characteristics based on what they needed. these are called acquired characteristics. (= NOT TRUE – or was he???????)

2. CHARLES DARWIN – an English naturalist who sailed for 5 years on the H.M.S. Beagle. The Beagle made many stops including at the Galapagos Islands. Darwin studied many species and determined that the great variety came from changes to the species over time.

-after his travels, Darwin wrote a famous book – The Origin of Species. In it, he had many very controversial ideas for how new species were created and how they changed over time.

3. EVOLUTION- the change in species over time. 4. NATURAL SELECTION-(=Darwin’s Theory) organisms with traits that are best suited to their environment will survive and pass on those beneficial traits to their offspring. (Survival of the fittest) Species = A group of individuals that can interbreed and produce fertile offspring.

-Darwin had seen “selection” in action in dog breeding. Those dogs with the most desirable traits were used for breeding. This is called artificial selection.

5. DARWIN’S FINCHES – Darwin noticed different types of species of finches. Each had a beak for its specific method of food gathering. -How is this evidence for natural selection?

6.The steps in natural selection: A.There is inherited variation within species. ?How does this variation come about?

b. There is overproduction of offspring each generation.

C. Resources are limited. there is a struggle for survival.

D. Only those individuals with the characteristics most beneficial in the environment are able to survive. they reproduce and pass on those beneficial traits.

*Adaptation – a structure or behavior that an organism has that allows it to survive in its environment. Structural Adaptations

Behavioral Adaptations

E. Each successive generation has a different gene pool because only those with beneficial genes are surviving.

F. Over time, a species becomes better adapted to that environment. Remember Ecology - environments don’t stay the same!

Red next to yellow – deadly fellow. Red next to black, friend of Jack! 7. Mimicry – Some organisms have developed adaptations that mimic traits of other species. In each, it helps them to survive in their environment.

8. Sexual Selection -A type of natural selection where organisms are favored (selected for) because of choices by the opposite sex.

WHAT CAN YOU CONCLUDE FROM THIS EXPERIMENT?

9. Genetic Drift – another method for evolution that is NOT natural selection.  A change in the allelic frequencies in a population that is due to chance  In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater.

10. Founder Effect  Occurs when a small sample of a population settles in a location separated from the rest of the population  Alleles that were uncommon in the original population might be common in the new population.

11. How Species Form -As populations move and/or the environment changes, populations can become split. This is c called speciation.

Geographic Isolation

11a. Geographic Isolation – when a barrier divides a population. Over long periods of time, the separate group’s dna has changed so much that they are now 2 different species.

-11b.Adaptive Radiation – population grows and spreads out. over time the are so spread out that different environmental factors affect different parts of the population. Therefore, new species are formed.

12. Gradualism- the idea that evolution occurs very slowly and gradually over long periods of time. 13. Punctuated Equilibrium- the idea that evolution occurs in spurts, with times in between with no change.

14. Types of Selection In a given population the distribution of a trait forms a bell-shaped curve on a graph. Example – Hand spread among students.

A.Stabilizing Selection - When selective pressures select against the two extremes of a trait, the population experiences a trend toward the “medium” Range of that trait. Example – Plant Height : Too short = not enough sunlight while too tall = fall over.

B. Directional Selection -one extreme of the trait distribution experiences selection against it. Example –Giraffes with short necks could not reach food in the trees and were “selected” against by nature.

C. Disruptive Selection - selection pressures act against individuals in the middle of the trait distribution Example – Different pollinators for short, medium and tall plants. If the pollinators of medium plants die off, the medium plants eventually die off. *What might this pattern lead to….?

15. Convergent Evolution - Unrelated species evolve similar traits even though they live in different parts of the world.

16. Divergent Evolution – Occurs as species that share close common ancestry eventually end up very different due to speciation.

1. Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium. Population Genetics

 This equation allows us to determine the equilibrium frequency of each genotype in the population.  Homozygous dominant (p 2 )  Heterozygous (2pq)  Homozygous recessive (q 2 ) 2. Hardy-Weinberg Equation:

How/Where did life begin? 1a.Scientists believe that life arose from nonliving matter. The earth was a violent place with a very different atmosphere billions of years ago. It may have been possible that life’s chemicals (list the 4 categories) could have formed spontaneously. 1b.With lipids for a membrane and RNA for genetic material, simple cells may have arisen in Earth’s oceans. 1c.UV light from the Sun and electric discharge in lightning might have been the primary energy sources.

 Stanley Miller and Harold Urey were the first to show that simple organic molecules could be made from inorganic compounds.  Later, scientists found that hydrogen cyanide could be formed from even simpler molecules in simulated early Earth environments.

3. Studies of fossils indicate that many forms have evolved from a few ancestral forms. 2. Simple prokaryotic cells may be the ancestors to all life on earth. 4. Eukaryotic cells may have evolved from prokaryotic cells as explained by the theory of endosymbiosis.

5. Evidence for Evolution: A. Fossils- traces of dead organisms. -fossils show that many organisms were different in the past and show that many species have gone extinct. -fossils also show intermediate steps in a species ancestry. -Most organisms decay before fossilization. Those that do fossilize happen to be in watery sediment that becomes sedimentary rock.

The deeper a fossil, the older it is.

B. Homologous Structures- similar structures in species that are not close ancestors. evidence suggests common ancestry.

C. Vestigial Structures- remnants from a species hereditary past.

D. Analogous Structures - the various structures in different species having the same appearance,species structure or function but have evolved separately, thus do not share common ancestor.ancestor

Analogous or Homologous?

E. Embryology- many diverse species have very similar embryo stages suggesting common ancestry. *Ontogeny = the development of an organism

F. Genetic/DNA Evidence The theory of evolution predicts that genes will accumulate more alterations in the nucleotide sequence over time -Therefore the closer the nucleotide sequence the...

6. Phylogenetic trees can show how closely species are related and where species branched away from each other.