Ch.12-14

Evolution Change in the inherited traits of a population of organisms from one generation to the next.

Who is this man and why are people still talking about him? 3

Charles Darwin Before Darwin During and After Darwin People believed that species were divine creations that were unchanging. Found evidence on his voyage on the Beagle he that challenged the traditional belief that species are unchanging. Darwin’s theory was that all species descended from earlier species. He called this Descent with Modification. Published his evidence in his book On The Origin of Species.

Galapagos Islands Darwin noticed many of the plants and animals of the Galapagos Islands resembled those of the nearby coast of South America 620 miles away. He concluded that they migrated there and changed after they arrived. See photo on p. 278.

Natural Selection Individuals with a physical or behavioral traits that better suit them to their environment are more likely to survive and reproduce than individuals who do not have those traits.

Factors of Natural Selection 1. All populations have genetic variation. 2. Environment presents challenges to successful reproduction. 3. Individuals tend to produce more offspring than the environment can support. 4. Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring than those that are less suited.

Species and Speciation Species A group of organisms that are closely related and can mate to produce fertile offspring. Subspecies – populations of same species that differ genetically due to adaptation to their environments. Speciation Process by which new species form.

Population All the individuals of a species that live in a specific geographical area and that can interbreed. In a population you can have variation, where members of the same species have differences.

Adaptation Feature that has become common in a population because the feature provides a selective advantage.

How Populations Evolve Gene pool – all the alleles (different versions of genes) in all the individuals of a population. Gene flow – exchange of genes with another population. Genetic drift – change in gene pool due to chance.

Artificial selection – intentional reproduction of individuals in a population that has desirable traits.

Geographic Isolation Physical barrier divides a population and they can no longer reproduce. May become separate species over time. Gene frequency changes more likely to occur in small population Different initial gene frequencies than main population. Different mutations occur within main pop and isolate them. Different environmental factors have different selection pressures on each population.

Reproductive Isolation Two populations of same species do not breed with one another because of a geographic separation. Ex. Darwin’s Finches and Australia’s marsupials

Phylogeny The evolutionary history of a species. Cladogram – diagram that shows ancestral relations between organisms..

Gradualism Model of evolution in which gradual change over time leads to new species.

Punctuated Equilibrium Periods of rapid change in species are separated by periods of little or no change.

Gradualism vs. Punctuated Equilbrium

Questions 1. The process by which a species becomes better adapted to its environment is called. A. Gradualism B. Adaptation C. Natural selection D. Reproductive isolation 2. The process by which isolated populations of the same species becomes new species is called. A. Speciation B. Reproductive isolation C. Genetic variation D. Natural selection

Questions 3. How does gradualism differ from punctuated equilibrium?

Evolution (whale) (human)

Evidence of Evolution Scientists agree that: 1. Earth is about 4.6 billion years old. 2. Organisms have inhabited Earth for most of its history. 3. All organisms living today share common ancestry with earlier, simpler life-forms.

Evidence Fossil Record Homologous and Analogous structures Comparative Biochemistry Comparative Cytology Comparative Embryology

Geologic Records Fossils – preserved remains of organisms that lived in past. Fossil record – collection of fossils recorded in rock layers over time. Extinct – species that no longer exist.

Paleontologists Scientist who study fossils. Age of fossils determined fairly accurately using radiometric dating. Have found intermediate fossils. Fishes and amphibians Reptiles and birds Reptiles and mammals. n/library/03/4/real/l_034_49.html n/library/03/4/real/l_034_49.html

Vestigial Structures Organs inherited but not used by modern organisms Present but greatly reduced in modern organisms Ex. Hip bone in python Appendix in human Tail bone (cocyx) in human Figure X-ray image of an atavistic tail found in a six-year old girl

Vestigial Structures

Homologous Structures Similar parts of different organisms that developed from the same ancestral body parts. Phalange Metacarpals Carpals Radius Ulna Humerus HumanCatWhale Bat

Analogous Structures Similar in purpose, but not inherited from a recent common ancestor Environment selected for trait Wings of birds and insects Convergent evolution

Homology Vs. Analogy

Convergent Vs. Divergent Evolution Convergent evolution – Unrelated species become similar due to same type of environment. Analogous structures Divergent evolution – Group from a specific population develops into a new species due to environmental conditions. Homologous structures

Comparative Biochemistry All life is based on organic chemistry Carbon based compounds All life uses same molecule as blueprint DNA Similar chemical processes Bacteria, algae, and plants all do photosynthesis Similar organisms have similar genetic code Humans and chimpanzees share nearly identical genes (98.4% identical gene sequences)

Comparative Cytology Endosymbiosis Theory that mitochondria are the descendants of symbiotic, aerobic eubacteria and chlor0plasts are descendants of symbiotic, photosynthetic eubacteria.

Comparing Embryos All vertebrate embryos, including humans, share features Eye spot Gill pouches Notochord Shows similar genetic ancestry Video real/l_042_02.html Video

Why do we care about evolution? Understanding where we came from. Bacteria Viruses e_s_6.html (antibiotic resistance) e_s_6.html l_011_20.html (AIDS) l_011_20.html

Questions 1. Anatomical structures that share a common ancestry are called ____________ structures. A. Vestigial B. Homologous C. Analogous D. Evolutionary 2. The process by which isolated populations of the same species become new species is called. A. Speciation B. Reproductive isolation C. Genetic variation D. Natural Selection