Evolution. Charles Darwin (English Scientist ) Ideas 1 st to be published HMS Beagle – South...
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Transcript of Evolution. Charles Darwin (English Scientist ) Ideas 1 st to be published HMS Beagle – South...
Charles Darwin (English Scientist )• Ideas 1st to be published• HMS Beagle – South America and South Pacific 5 year journey– Organism diversity led to curiosity about relations– Galapagos• Species-unique but similar• Led to idea of change over time (spent 22 years
studying)
• Ideas supported by fossil evidence
Galapagos Unique Adaptations
• Galapagos finch – Beak feed on Cacti
• Galapagos Tortoises– Largest in body size and shape
• Galapagos marine iguanas– Eat algae on ocean bottom (unusual food for
reptile)– Large Claws-slippery rocks
Charles Darwin• Base on Thomas Malthus idea “Human
population grows faster than Earth’s food supply” Darwin realized organisms:– Struggle to survive– Struggle for food– Compete for space– Escape predators– Find mates– Find shelter
Darwin and pigeons
• Breed and watched survival• Traits--vary depending on size and inheritance• Artificial Selection-breed organisms with
specific traits
Darwin and Natural Selection
• Mechanism for change in population• Organisms with certain variations, survive,
reproduce, and pass their variations to next generation.
• Organisms without variations less likely to survive and reproduce.
Natural selection gradual process by which biological traits become either more or less common in a population as a function of the effect of inherited traits on the differential reproductive success of organisms interacting with their environment.
Darwin-how species change over time
• Organism produce more organisms than can survive (fish millions of eggs)
• Individuals in a population have variations (different color, size, speed)
• Individuals with useful variations survive and pass traits (speed)
• Overtime-offspring with certain variations make up most of population and may look different from ancestors.
Darwin
Determined that species did not arise independently; rather species are
descendants of other species.
Alfred Russell Wallace
• Studied in Indonesia and Amazon River• Introduced Theory of Evolution• “Useful variations will tend to increase, un-
useful or hurtful variations to diminish”• Some qualities of an individual may allow it to
outlive another w/o qualities; pass qualities to offspring.
Lamarck’s Model
• Jean Baptiste de Lemarck• Individuals change due to environmental
influences; organisms adapt based on individual needs
• Acquired changes passed to offspring• “Use and disuse”- stronger is used; weaker if
not used; overtime modified due to use or disuse; disuse may disappear.
Relationship of work by Lamarck, Wallace and Darwin
• Darwin refuted Lamarck’s hypothesis that individuals change to meet needs due to environmental stress and that these acquired characteristics
• Wallace work overshadowed by Darwin; Now some celebrate Wallace more– Jointed presented to scientific community
Visualizing EvolutionEvolution difficult to observe– Short scale of human life– Contradictory to faith– Interpretations of data
Mimicry—Structural adaptations that enables one species to resemble another.
• Batesian- a species without any special defense mechanism mimics another species that predators avoid. (Same warning signs –coloring, pattern—no defenses—chemicals, spines)• Mullerian- more than one species with similar defense
mechanisms all have the same coloration (Same warning signs and same defenses)
Darwin’s idea of natural selectionex Mole Rat
• Current animals probably resemble African rock rats
• Ancestors avoided predators-size of teeth and claws
• Ancestors survived passes variations to offspring
• Over time-modern mole rat—blindness evolved b/c no survival advantage.
Physiological Adaptations-(some rapid)
• Changes in metabolic process– Bacteria that resist antibiotics– Insects and weeds resistant to chemicals that kill
them.
Fossils
• Record of early life and evolutionary history
• Still incomplete record-jigsaw puzzle
• As become more complete, sequence of evolution more clear
Anatomy• Homologous
Structures-structural features with a common evolutionary origin
• Similar arrangement or function or both
Anatomy
• Analogous (aka “convergent”) Structures-Do not have common evolutionary (evolved independently) origin but similar in function
Anatomy
• Vestigial Structure-Body structure with no function in present day organism (ancestor’s may have used)– Eyes on blind mole-rat and cave fish– Forelimbs of ostrich
Embryo
• Earliest stage of growth and development of plants and animals.
• Similarities among young embryos suggest evolution from a distant, common ancestor.
Biochemistry
• DNA and RNA comparisons• Determine evolutionary relationships b/w
species• 1970s RNA and DNA nucleotide sequencing to
construct evolutionary diagrams.
Mechanism for Genetics and Evolution
• Genetics used to explain variation among individuals of a population
• Studies of the complex behavior of genes in populations-population genetics
• Populations, not individuals evolve.
Genetic equilibrium
Population in which the frequency of alleles remains the same over generations
• Affect small populations• Observed in small human populations that
have been isolated• Can result in an increase of an allele in a small
population (Amish)
Genetic Equilibrium Disturbances
• Gene Flow-transport of genes by migrating individuals– Leaves-genes lost from gene pool– Enter-genes added to gene pool
• Mutations, genetic drift and gene flow may significantly affect the evolution of small and isolated gene pools (island)
• Natural selection most significant factor to change a gene pool.
Natural Selection acts on variations
• Variations can be inherited and they are controlled by alleles
• Allelic frequencies in a pop’s gene pool will change over generations due to natural selection.
• Three types of natural selection: Stabilizing, directional and distruptive
Speciation
• When members of similar populations no longer interbreed to produce fertile offspring within natural environment.– Geographic isolation– Reproductive isolation– Polyploid
Geographic isolation
• Physical barrier divides population– Prevents interbreeding between 2 groups
• Founders Effect