Charles Darwin• developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors. – The process of change over time is called evolution.
Species Vary Globally• different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe.• Rabbits that live in the grasslands in England don’t live in the grasslands in Africa!• Do we have Kangaroo’s living in the wild in the US?
• flightless, ground- dwelling birds called • Ostriches rheas living in the only live in grasslands of South Africa America• look and act a lot like ostriches.• Only live in South Africa • Emu’s only live in Australia
Species vary Locally– different, yet related, animal species often occupied different habitats within a local area.
Turtles in Galapagos• All the Islands have different climates – Isabel Island has high peaks, is rainy, and has abundant vegetation that is close to the ground. – A tortoise from Isabela Island has a dome-shaped shell and short neck. – Hood Island, in contrast, is flat, dry, and has sparse vegetation. – A long neck and a shell that is curved and open around the neck and legs allow the Hood Island tortoise to reach sparse, high vegetation.
Species Vary over Time– Darwin also collected fossils, which are the preserved remains or traces of ancient organisms.– Darwin noticed that some fossils of extinct animals were similar to living species.
Charles Lyell-uniformitarianism- theidea that the geologicalprocesses we see inaction today must bethe same ones thatshaped Earth millions ofyears ago. -Volcanoes -rivers dig canyons and channels
Niagra Falls• The force of the water wore away the rock layers and Niagara Falls moved upstream, eventually reaching its present location.• Gradual erosion and periodic rockfalls steadily move Niagara Falls farther upstream
Jean Baptiste Lamark • organisms could change during their lifetimes by selectively using or not using various parts of their bodies • individuals could pass these acquired traits on to their offspring, enabling species to change over time.
Lamarck• All animals strive to become perfect? – NOT TRUE!!!!!• inheritance of acquired characteristics- traits acquired during a lifetime can be passed on to offspring – NOT TRUE!!!!!!
Thomas Malthus• If the human population grew unchecked, there wouldn’t be enough living space and food for everyone
Darwin Thinks about Malthus– reasoning applied even more to other organisms than it did to humans.– most offspring die before reaching maturity, and only a few of those that survive manage to reproduce.
Neo-Darwinism• Natural selection chooses the most advantageous traits for an organism so that those traits are passed on to future generations – DOES NOT CREATE NEW GENES• Mutations cause the changes in genes and account for the variety of life today• Darwins theory of evolution was revised to include our knowledge of geneticts. The revised theory is Neo-Darwinism.
The First Cells• Autotrophs were the first cells – Photosynthetic- convert CO2 & water to glucose – Chemosynthetic-live in extreme environments• Scientists believe that the presence of photosynthetic bacteria helped to form the atmosphere as we know it today
• Oxygen would hurt Anaerobic cells• Anaerobes must have evolved into Aerobic cells to use the excess oxygen to produce energy• This leads us to the…..
Endosymbiotic Theory• A large anaerobic primitive cell engulfed an aerobic prokaryote to form a symbiotic relationship with it.• This bacterium may have become a mitochondrion over time (have their own DNA, divide by binary fission)• This symbiotic relationship resulted in the first aerobic eukaryote.• All other eukaryotic cells evolved from this cell.
Natural Selection- describes how organisms that are best adapted to their environment survive and reproduce
Elements of Natural Selection1. All species have genetic variation2. Individuals within a species frequently compete with each other for survival3. The environment presents challenges to an organisms survival4. “survival of the fittest”5. The traits of an organism best suited to a habitat tend to become more frequent in a population over time
Species• Similar organisms that can interbreed and produce fertile offspring
Population• Made of organisms of the same species that live in the same place at the same time
Think About it!• Let’s suppose that a wild rabbit population that lives in a densely wooded area has genes that can produce white offspring, brown offspring or black offspring. How could environmental factors and natural selection affect which trait for fur color occurs most often?
Stabilizing Selection• When natural selection favors average individuals• Insects want to be average size – BIG insects are more likely to be consumed – Tiny insects can’t capture their food
Directional selection• Favors an organism with an extreme trait• Galapagos Finches – During a drought food became scarce the finches with larger beaks were better suited for survival
Disruptive Selection• Favors organisms with extremes in both directions and eliminates the traits in the middle• If there was only really small bird seed and really big bird seed, then only birds with really tiny beaks and really big beaks would thrive!
Hmmm…..• In humans, infants with a low birth weight or with a high birth weight are less likely to survive. Which type of natural selection is seen in the birth weight of humans?• Lets suppose that the wild rabbits living in a heavily wooded area have genes for various shades of brown fun color. If a mutation occurs to produce offspring that are albino, would the mutation be harmful or beneficial?
Adaptations• Specific characteristics that help animals survive in their environment• Can be physical or behavioral• Cats have claws to catch prey, pointed teeth to tear apart food.
Critical Thinking• A mutation occurs in a plant that causes its leaves to taste bitter. In what kind of environment would this mutation be beneficial and more likely passed on to future generations?
Importance of Diversity• Diversity- a variety of traits that might be passed on from generation to generation• Gene pool- the total number of genes that account for different traits in a species• Species with a large gene pool have more diversity and a greater ability to adapt• A small gene pool limits diversity and can traits can be lost for a number of reasons
Reason #1- Natural Selection• Environmental factors often favor some genetic characteristics over others• Specific traits may be favored over others to the point that undesirable traits can no longer be found
Reason #2- Genetic Drift• Change in a gene pool generated by chance• Instead of the environment selecting a trait mere chance causes one trait to occur more often than others• Occurs more often in small populations
Reason #3- Founder effect• The threat of extinction causes very few organisms to be available to mate• If the species recovers only the genes in the limited gene pool get passed on• The new gene pool may favor a different trait than the original population
Reason #4- Selective Breeding• Humans can use artificial selection through selective breeding• Wheat used to grow wild and had large diversity• Farmers chose the wheat plants that grew the best and the “undesireable” traits decreased• Wheat is now uniform but subject to diseases and pests
Reason #5- Mutations• Add genetic variation• In a stable environment they may be harmful or have no benefit• In a changing environment they may allow an organism to adapt
Antibiotic and Pesticide Resistance• Bacteria mutate easily and as a result bacteria acquire antibiotic resistance in only a few generations.• Mosquitoes are resistant to DDT
Speciation• The beginning of a new species and occcurs when members of populations no longer inbreed
Geographic Isolation• When an event creates a physical barrier that divides a population into 2 or more separate groups.• Volcanic Eruptions or separation of a land mass
Temporal Isolation – When a species develops different reproductive cycles ( ex. A spring and fall cycle)• Spring breeders will not breed with fall breeders and the 2 groups slowly drift apart
Behavioral Isolation• Occurs when 2 populations do not interbreed because of differences in courtship behaviors.• 2 similar species of birds may be capable of producing fertile offspring but because of different mating songs they will not interbreed
Relative Dating• Dating of fossils tells which fossils are older than other fossils based on where they are found in sedimentary rock layers• The farther down the older Radiometric Dating• Tells the approximate age of a fossil by measuring the amount of radioactive isotopes found in the fossil.
Punctuated Equilibrium• Suggests that long intervals in which little or no change occurs are suddenly interrupted by short bursts of quick, radical transitions.• Scienctists now believe in a combination of gradual and punctuated
Comparative Anatomy• Homologous-develop from the same tissues as embryos and have similar internal structures – Common structures• Analogous- have similar functions but have not evolved from the sam ancestor
Comparative Anatomy• Vestigal Structures- structures that seem to have no useful purpose now but resemble useful structures in other animals – Ostrich wings, cave salamander eyes• Embryology-embryos of many vertebrates look similar – If the embryos look alike they might have the same ancestors
Biogeography• How plants and animals are distributed around the world• Depends on migration patterns• The distribution is used to figure out how and when species may have evolved
Divergent Evolution• New species “diverge” or split from a common ancestor – Homologous structures are evidence – Adaptive radiation- one ancestorial species splits into many related species • Darwin’s Finches
Convergent Evolution• Organisms that have similar characteristics but are not considered closely related – Sharks and porpoises – Analogous structures are evident
Coevolution• When 2 organisms are dependent on one another for survival – Flowering plants and the specific insects that pollinate them
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