Early atmosphere evidence natural selection and disease agents influence natural selection Introduction Evolution simple definition change over time Evolution helps us to understand the history of life ID: 912623
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Slide1
Theory of Evolution
Just how do species change over time????
Early atmosphere, evidence, natural selection and disease agents influence natural selection.
Slide2Slide3Introduction
Evolution “ simple” definition: change over time
Evolution helps us to understand the history of life.
Slide4The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother
Central idea
Slide5Adaptations
Fossil Record
Comparative Anatomy
Embryological Development
DNA Similarities
Evidence for Evolution
Slide6All organisms have adaptations which help them survive in their particular environment
Adaptation
: a structure or behavior that helps an organism better survive in its environment
Examples: Mimicry, camouflage and physiological
Adaptations
Slide7Slide8Mimicry
Mimicry
: a structural adaptation that enables one species to resemble another species
E.g. A harmless species might mimic a poisonous one
Slide9Slide10Slide11Slide12Camouflage
Camouflage
: a structural adaptation that allows a species to blend in with its surroundings
Slide13Slide14Slide15Slide16Slide17Many bacteria have evolved resistance to antibiotics in the last 50 yearsPests have evolved resistance to pesticides
Physiological Adaptations
Slide18Pathogens can influence natural selection by weeding out the weaker ones
Organisms
with stronger immune systems are more likely to survive pathogens.
Eventually
, the species that builds up antibodies for this particular pathogen will thrive
.
Bacteria are also affected by Natural Selection.
The
bacteria that build up a resistance the antibiotics
survive.
T
he
ones that do not also die, just like in animals and
plants
.
Pathogens a bacterium, virus, or other microorganism that can cause disease
Slide20https://www.youtube.com/watch?feature=player_embedded&v=zjR6L38yReE
http://
www.pbs.org
/
wgbh/evolution/library/10/4/quicktime/l_104_03.html
Slide21Variation in Populations
Evolution by natural selection happens in populations, not individuals. A single organism cannot evolve. Populations evolve.
Inheritable
characteristics are traits you are born with.
Populations evolve because there is variation
Variation causes some organisms to be better fit than others. These better fit organisms are more likely to survive and pass their genes to the next generation
Slide22Slide23Evolution
is the gradual change in a population over time
Darwin was the first scientist to realize that evolution can work by
natural
selection.Natural Selection – Organisms with traits well suited to an environment are more likely to survive and produce more offspring than organisms without these favorable traits
“
Survival of the fittest
”
E.g. Thicker fur is a favorable trait in cold environments
Evolution by Natural Selection
Slide24Slide25Slide26Slide27English naturalist who proposed the theory of evolution by natural
selection
Charles Darwin (1809 – 1882)
Slide28Darwin sailed around the world on the HMS Beagle and carefully studied thousands of different plants and animals
HMS Beagle Voyage
Slide29On the Galapagos Islands Darwin found very strange plants and animals that don’t exist anywhere else in the world!
The Galapagos Islands
Slide30Slide31Different islands have different types of finches not found on any other islands. This is where species all deriving from a common ancestor have over time successfully adapted to their environment via natural selection.
Darwin’s Finches
Slide32Two Types of Evolution
Convergent evolution
: distantly related organisms evolve to become more similar
Happens when unrelated species adapt to
similar environments, possibly in different parts of the world
Slide33Slide34Divergent evolution: species that once were similar become increasingly different
Happens when populations adapt to
different
environments
Two Types of Evolution
Slide35Slide36Galapagos Giant Tortiose
Slide37Blue-footed Booby
Slide38Slide39Slide40Natural Selection
There are 3 basic types of natural selection
Directional Selection
Stabilizing Selection
Disruptive Selection
Slide41Directional Selection
Directional selection
: favors one of the extreme variations of a trait
E.g. Male peacock tail feathers: Females favor larger tail feathers. Therefore males with larger feathers reproduced more often. Over many generations tail feathers grow larger and larger
Slide42Slide43Slide44Stabilizing selection: favors average individuals in a population
E.g. Human infants: Too small = bad; too large = bad; average = good
Stabilizing Selection
Slide45Slide46Disruptive Selection
Disruptive selection
: favors individuals with either extreme of a trait but intermediate individuals have a disadvantage
E.g.
Cuddlefish (a type of squid): Being large is an advantage because females prefer larger males. Being small is an advantage also. Small males impersonate females trick the females into mating.
Slide47Slide48Atmosphere contained all of the following gases:
Nitrogen
Ammonia
Methane
Carbon Dioxide
Water
Hydrogen
No oxygen….oxygen came
later
with photosynthesis.
Early Atmosphere conditions
Slide49Slide50Endosymbiotic Theory
https://www.youtube.com/watch?v=FGnS-Xk0ZqU
is an evolutionary theory of the origin of eukaryotic cells from
prokaryotic organisms
Remember the webquest you did!
Slide51How did the first cells evolve?
Experiment conducted by
Miller and Urey
proposed simple- organic molecules could have been synthesized in the atmosphere of early Earth and rained down into the oceans.
Slide52Fossil: Any trace of a dead organism
Fossils show the evolution of species over the past millions of years
Fossil evidence proves that modern species have evolved from ancient species
Fossil Evidence
Slide53Puijila the walking seal
Slide54Tiktaalik
Slide55Archaeopteryx
Slide56Slide57Comparative Anatomy
Homologous structures
: Body structures on different organisms that are
similar in structure
(same bones) and evolved from a common ancestor
Slide58Homologous Structures
Slide59Comparative Anatomy
Analogous structures
: Body structures on different organisms that are
similar in function
but did not evolve from the same ancestor (bird wing and butterfly wing)
Slide60Analogous Wing Structures
Moth (insect)
Pterodactyl (reptile)
Bird
Bat (mammal)
Slide61Comparative Anatomy
Vestigial structure
: body structure in an organism that no longer serves its original purpose but was useful to an ancestor (useless wings on the African ostrich)
Slide62Slide63Slide64Slide65Embryological Development
Early in development, human embryos and embryos of all other vertebrates are very similar, which suggests that all vertebrates are related
Slide66Slide67DNA Similarities
Nearly all organisms have DNA, ATP, and many of the same proteins and enzymes
The DNA (genes) of closely related organisms looks very similar
Slide68What Drives Evolution?
Mutations
Genetic Drift
Gene Flow
Natural Selection
Slide69Gene Pool
Gene pool
: collectively, all of the alleles of the population’s genes
Allelic frequency
: the percentage of any specific allele in the gene poolGenes can enter and leave a population’s gene pool for many reasons
Populations in which the gene pool is not changing are said to be in
genetic equilibrium
Slide70Genetic Drift
Genetic drift
: when gene frequencies are changed by random events in a isolated population
Example: diseases, natural disasters, mating habits
Slide71Genetic drift can cause big losses of genetic variation for small populations.
population's
size is reduced for at least one
generation
Reduced genetic variation means that the population may not be able to adapt to new selection pressures, such as climatic change or a shift in available resources, because the genetic variation that selection would act on may have already drifted out of the population.
Bottleneck Effect
Slide72Slide73Gene Flow
Gene flow
: the transport of genes by traveling individuals
When an individual leaves a population, its genes are lost from the gene pool
When an individual enters a population, its genes are added to the gene pool
Slide74Slide75Mutations
New genes can be added to the population by errors in DNA copying called
mutations
Most mutations are neutral or bad!
Slide76Slide77Mutations
Very very rarely a mutation might come along that improves an organism’s chance at survival or reproduction
These mutant genes will be passed along to offspring and become more common in the gene pool over time
If the mutation offers a large advantage, eventually (after many generations) all members of the population will have the beneficial mutation
Slide78Slide79Slide80Artificial Selection: Humans choose individuals with certain traits for breeding
After many generations of selection, dramatic evolutionary changes can result
Dogs
Fruits/Vegetables
Livestock
Evolution by Artificial Selection
Slide81Slide82Slide83Speciation-the evolution of a new species
A certain population may become isolated and evolve to fit new or different environmental conditions
The isolated population may change so much that it can no longer mate with the original population
Similar to the evolution of new languages
Slide84Slide85Slide86How Fast Does Speciation Occur?
Gradualism
: idea that species originate through a gradual change of adaptations (longer than 10,000 years)
E.g. Fossil evidence shows that sea lilies evolved slowly and steadily over time
Punctuated equilibrium: idea that species originate in rapid bursts (10,000 years or less) with long periods of genetic equilibrium in between
Global ice age causes rapid adaptation of thick fur
Both gradualism and punctuated equilibrium are known to occur