Objective 11 - Evidence for the modern theory of evolution
Biogeography - p. 663
– study of the geographical distribution of species.
•Animals on islands evolved from mainland migrants
• he populations adapt over time to adjust to environmental conditions of their new home.
•Geographically close environments are more likely to be inhabited by similar species than locations that are geographically separate but environmentally similar (desert in Africa and desert in Australia have vastly different organisms) (these were Darwin’s ideas)
•https://www.youtube.com/watch?v=cC8k2Sb1oQ8 ~ 11 min
Fossil Record (p.659)– remains and traces of past life found in sedimentary rock, which has layers that correspond to time periods.
•reveals the history of life on earth
•Shows the kinds of organisms that were alive in the past.
A little background on formation of fossils (FYI):
•Fossils form in sedimentary rock
•Soil and rock particles are laid down at the bottoms of lakes and oceans. Gradually newer layers are formed over older ones, and the layers
compress and harden
•Fossils in lower layers are older than those in upper layers.
•Younger fossils look more like modern organisms
•Fossils appear in chronological order
•All organisms weren’t present 3.5 billion years ago; this indicates that species evolved from earlier forms.
•Transitional fossils – shows characteristics between two groups of separate organisms.
Ex. Archaeopteryx – had teeth, claws on it’s wings and a tail like a reptile, but feathers like a bird.
Comparative Anatomy (p. 664-665)– when studying anatomy of different animals, some show a similar ancestry
•Limbs of humans, frog, bat, porpoise, & horse
•All have the same basic arrangement of bones.
•However, modified into wings, arms, legs, fins.
•Homologous structures – body parts in different species have the same evolutionary organism, but have different structure and function.
Just because two organisms have structures that perform the same function, doesn’t mean they are closely related.
•Analogous structures – body parts in different species that have a similar function, but evolved
separately (insect wings and bird wings)
Some organisms have structures that no longer serve a function, but were functional in the ancestors of that organism – vestigal structures.
•baleen whale – vestigal pelvic bone (these bones serve no purpose for the whale, as they have no hind limbs).
•Forelimbs of the flightless ostrich (their ancestors were probably able to fly)
Comparative Embryology – study of embryos of different species look similar during early of development
•All vertebrate embryos have a gill pouch at some stage, and a tail.
•Ex. Fish, birds mammals and reptiles are very similar in the early stages
•As they evolve, they become dissimilar (gill pouch becomes gill in fish, but modifies to eustacian tube in humans; fish develop tail, but tail in humans becomes the coccyx (bone at the end of the spine)
Heredity – the laws of inheritance can explain the variations in organisms that enable natural selection to take place.
Showing that traits are passed and mutations occur reveal how a species can change.
Molecular Biology – by comparing DNA and proteins among organisms it can be determined how closely related they are.
•By studying DNA, it shows that dogs are related to bears.
•Whales are dolphins are related to ungulates (hoofed mammals like cows and deer)
•Humans and chimps have a 2.5% difference in DNA
•Humans and lemurs have 42% difference
•Able to link all organisms back to earlier species based on common proteins.
•Ex. Cytochrome c protein in mitochondria
•Mitochondria resemble bacteria
•Chloroplasts similar to cyanobacteria (blue-green algae)
Biogeography - p. 663
– study of the geographical distribution of species.
•Animals on islands evolved from mainland migrants
• he populations adapt over time to adjust to environmental conditions of their new home.
•Geographically close environments are more likely to be inhabited by similar species than locations that are geographically separate but environmentally similar (desert in Africa and desert in Australia have vastly different organisms) (these were Darwin’s ideas)
•https://www.youtube.com/watch?v=cC8k2Sb1oQ8 ~ 11 min
Fossil Record (p.659)– remains and traces of past life found in sedimentary rock, which has layers that correspond to time periods.
•reveals the history of life on earth
•Shows the kinds of organisms that were alive in the past.
A little background on formation of fossils (FYI):
•Fossils form in sedimentary rock
•Soil and rock particles are laid down at the bottoms of lakes and oceans. Gradually newer layers are formed over older ones, and the layers
compress and harden
•Fossils in lower layers are older than those in upper layers.
•Younger fossils look more like modern organisms
•Fossils appear in chronological order
•All organisms weren’t present 3.5 billion years ago; this indicates that species evolved from earlier forms.
•Transitional fossils – shows characteristics between two groups of separate organisms.
Ex. Archaeopteryx – had teeth, claws on it’s wings and a tail like a reptile, but feathers like a bird.
Comparative Anatomy (p. 664-665)– when studying anatomy of different animals, some show a similar ancestry
•Limbs of humans, frog, bat, porpoise, & horse
•All have the same basic arrangement of bones.
•However, modified into wings, arms, legs, fins.
•Homologous structures – body parts in different species have the same evolutionary organism, but have different structure and function.
Just because two organisms have structures that perform the same function, doesn’t mean they are closely related.
•Analogous structures – body parts in different species that have a similar function, but evolved
separately (insect wings and bird wings)
Some organisms have structures that no longer serve a function, but were functional in the ancestors of that organism – vestigal structures.
•baleen whale – vestigal pelvic bone (these bones serve no purpose for the whale, as they have no hind limbs).
•Forelimbs of the flightless ostrich (their ancestors were probably able to fly)
Comparative Embryology – study of embryos of different species look similar during early of development
•All vertebrate embryos have a gill pouch at some stage, and a tail.
•Ex. Fish, birds mammals and reptiles are very similar in the early stages
•As they evolve, they become dissimilar (gill pouch becomes gill in fish, but modifies to eustacian tube in humans; fish develop tail, but tail in humans becomes the coccyx (bone at the end of the spine)
Heredity – the laws of inheritance can explain the variations in organisms that enable natural selection to take place.
Showing that traits are passed and mutations occur reveal how a species can change.
Molecular Biology – by comparing DNA and proteins among organisms it can be determined how closely related they are.
•By studying DNA, it shows that dogs are related to bears.
•Whales are dolphins are related to ungulates (hoofed mammals like cows and deer)
•Humans and chimps have a 2.5% difference in DNA
•Humans and lemurs have 42% difference
•Able to link all organisms back to earlier species based on common proteins.
•Ex. Cytochrome c protein in mitochondria
•Mitochondria resemble bacteria
•Chloroplasts similar to cyanobacteria (blue-green algae)
Objective 12 - How Mendel’s work and the idea of mutations supported Darwin
•Mendel revealed that genes do not blend in offspring and that genes retain their
characteristics when passed to offspring
•It’s these genes that are either inherited or not, based on how suited they are to
the environment in which an organism lives (natural selection)
Mutations
•There are variations in a population due to mutations as well
•Can occur randomly or genetically
•If the mutations were‘good’ an organism could be at a great advantage (think of the
1 in 1 million bacteria that’s resistant to a pesticide)
•Darwin, of course saw variations in a species as he travelled from place to place (finches), and how new species could rise from ancestral ones.
Modern synthesis – Modern combination of Mendel’s and Darwin’s theories of evolution.
Evolution – the relative change in the characteristics of populations that occurs over successive generations
Objective 13 - Modern Theory of evolution and it's importance to biological sciences
•New variants of species arise in populations
•Come from crossing over and mutations
•These traits/genes can be passed onto offspring
•Will thrive if variants enable or do not affect the survival of an organism in a particular setting
•Variations enable a population to survive during environmental changes.
•Those best suited are ‘selected’ to survive.
•These genes are passed on to some of the offspring which increase their likelihood of
survival
Great example - see finches below.
•Mendel revealed that genes do not blend in offspring and that genes retain their
characteristics when passed to offspring
•It’s these genes that are either inherited or not, based on how suited they are to
the environment in which an organism lives (natural selection)
Mutations
•There are variations in a population due to mutations as well
•Can occur randomly or genetically
•If the mutations were‘good’ an organism could be at a great advantage (think of the
1 in 1 million bacteria that’s resistant to a pesticide)
•Darwin, of course saw variations in a species as he travelled from place to place (finches), and how new species could rise from ancestral ones.
Modern synthesis – Modern combination of Mendel’s and Darwin’s theories of evolution.
Evolution – the relative change in the characteristics of populations that occurs over successive generations
Objective 13 - Modern Theory of evolution and it's importance to biological sciences
•New variants of species arise in populations
•Come from crossing over and mutations
•These traits/genes can be passed onto offspring
•Will thrive if variants enable or do not affect the survival of an organism in a particular setting
•Variations enable a population to survive during environmental changes.
•Those best suited are ‘selected’ to survive.
•These genes are passed on to some of the offspring which increase their likelihood of
survival
Great example - see finches below.
Objective 14-17 - Hardy Weinberg.
•Population genetics - the study of changes in gene frequencies in population of organisms and the effects of such changes on evolution and adaptation.
•Gene pool – the total of all genes in a population at any one time
•Allele frequency – the presence of an allele in a population.
•Hardy Weinberg principle -theory stating that in the absence of forces that change the proportions of the alleles at a given locus, the original genotype proportions will remain constant from one generation to the next, in a large population with random mating.
•Hardy-Weinberg Equilibrium - condition of a population in which genotypes of members maintain the same proportions through several generations.
Five conditions to maintain Hardy Weinberg Equilibrium
•Random mating - females cannot select males... each male is as likely as the other to be selected as a mate (like names drawn from a bag).
•No mutations - alleles must remain unaltered
•Isolation - no mixing of populations.
•Large population size - population must be large
•No natural selection - no genotype has a reproductive advantage over the other.
Natural populations cannot meet all of the criteria listed above. Therefore, Hardy-Weinberg equilibrium cannot exist.
Significance in the development of evolutionary theory: One way to determine how real population does change is to develop a model of a
population that does not change genetically from one generation to the next and compare ACTUAL populations with this model.
Work Sheet provided for practise-problems relating to Hardy-Weinberg Equilibrium.
http://www.weebly.com/weebly/userHome.php - Hardy Weinberg tutorial (~11 mins)
Things that can disrupt Hardy-Weinberg Equilibrium:
1. mutations - a mutation that alters the DNA can be passed on to offspring. If it provides a selective advantage, it may result in individuals producing a disproportionate number of offspring as a result of natural selection. The favorable mutation will appear with greater frequency in the population.
Ex. Mosquitoes resistant to insecticide; bacteria resistant to antibiotics
2. genetic drift - (genes drift out of a population) The change of frequencies of a particular allele in a small population can be changed drastically by chance alone. Since not all organisms reproduce in a population, there’s a chance of some traits being lost (drifting out of the population).
After that allele is gone, gene pool gets smaller.
Two types of genetic drift
•bottleneck effect - occurs when a population is greatly reduced by events such as natural disaster or overhunting, resulting in certain alleles being overrepresented and other alleles being underrepresented or absent in the population, due to chance. Genetic variation in the surviving
population is reduced.
•Ex. Northern elephant seals. Overhunting. Surviving seals are protected, and increased in population again, but contain fewer variants in the alleles.
•Ex. Whooping cranes. 177 in Wood Buffalo National Park NWT thought to have come from 6-8 parents. Loss of diversity.
•founder effect (new species found) - cause of genetic drift due to a small group of individuals colonizing a new area. The small
group probably will not contain all the genes represented in the parent population.
•Ex. Hawaiian honeycreepers. Migrated from North America, inhabited several islands, and each population evolved into a different species, beginning with very few ‘parents’
•Ex. Human populations with founder effect have high incidence of genetic disorders. Newfoundland is an example of this.
•Ex. Small village in Venezuela has high incidence of Huntington’s.
3. gene flow - movement (or flow) of new genes into a gene pool.
This movement can reduce difference between populations that were caused by isolation and genetic drift.
•Ex. A windstorm or tornado can deliver new seeds to an area, resulting in new alleles into a gene pool if populations mix.
4. non random mating - Genetic equilibrium is maintained if there is no organized means to mate selection (completely random).
Often people in close proximity are more likely to mate than those more distant in a population (if one person moves away, the other is more likely to
find someone new who is still in the area).
•Inbreeding - mating between closely related partners. Results in a population with more homozygous individuals (mating between purebred dogs of same family).
•assortive mating - Individuals choose partners of similar phenotype (such as size). Ex. Many animals, like toads, choose a partner of similar size. This is the basis of artificial selection, and can result in decrease in genetic diversity.
5. natural selection - all animals are not equal in their ability to survive and reproduce. Some offspring leave more offspring than others.
There are selective pressures such as predation and competition, so those best suited to the environment are more likely to survive and reproduce, going against Hardy-Weinberg.
Three ways natural selection can affect the frequency of a heritable population:
stabilizing selection - natural selecton that favors intermediate phenotypes and acts against extreme variants (likes the
stable and predictable rather than the rebels ;) This reduces variation, as less are on the extremes.
•Ex. Babies born of “middle scale” weight are more likely to survive, than bigger or smaller babies. Over time, less and less bigger or smaller babies are born and more “middle of the road” babies are born (p. 693)
directional selection - favors the phenotypes at one extreme over the other, resulting in the distribution curve of phenotypes shifting in the direction of that extreme. This situation often occurs when there’s a time of environment change or species migrate to a new habitat (the most popular form moved in the direction of one of the extremes)
•Ex. Ancestral horses were smaller and had a forest habitat. When forests were replaced by grasslands, larger horses were more suitable for the environment based on durable teeth and longer legs for increased speed in the open area.
Other examples: the peppered moth, insect resistance to pesticides, bacterial resistance to antibiotics.
Disruption (diversifying) selection- opposite of stabilizing selection. When the extremes of phenotypes are favored rather than the
intermediate.
•Ex. Small salmon and large salmon are more likely to survive over medium sizedsalmon. Can eventually result in
only small and large salmon (no medium)
6. sexual selection. Selection for mating based on competition between males and choices made by
females.
•Ex. Plummage of peacock, fighting between males, Larger mane of a lion, bigger antlers of a moose. The ‘better’ male is more likely to be selected for sexual reproduction.
•Population genetics - the study of changes in gene frequencies in population of organisms and the effects of such changes on evolution and adaptation.
•Gene pool – the total of all genes in a population at any one time
•Allele frequency – the presence of an allele in a population.
•Hardy Weinberg principle -theory stating that in the absence of forces that change the proportions of the alleles at a given locus, the original genotype proportions will remain constant from one generation to the next, in a large population with random mating.
•Hardy-Weinberg Equilibrium - condition of a population in which genotypes of members maintain the same proportions through several generations.
Five conditions to maintain Hardy Weinberg Equilibrium
•Random mating - females cannot select males... each male is as likely as the other to be selected as a mate (like names drawn from a bag).
•No mutations - alleles must remain unaltered
•Isolation - no mixing of populations.
•Large population size - population must be large
•No natural selection - no genotype has a reproductive advantage over the other.
Natural populations cannot meet all of the criteria listed above. Therefore, Hardy-Weinberg equilibrium cannot exist.
Significance in the development of evolutionary theory: One way to determine how real population does change is to develop a model of a
population that does not change genetically from one generation to the next and compare ACTUAL populations with this model.
Work Sheet provided for practise-problems relating to Hardy-Weinberg Equilibrium.
http://www.weebly.com/weebly/userHome.php - Hardy Weinberg tutorial (~11 mins)
Things that can disrupt Hardy-Weinberg Equilibrium:
1. mutations - a mutation that alters the DNA can be passed on to offspring. If it provides a selective advantage, it may result in individuals producing a disproportionate number of offspring as a result of natural selection. The favorable mutation will appear with greater frequency in the population.
Ex. Mosquitoes resistant to insecticide; bacteria resistant to antibiotics
2. genetic drift - (genes drift out of a population) The change of frequencies of a particular allele in a small population can be changed drastically by chance alone. Since not all organisms reproduce in a population, there’s a chance of some traits being lost (drifting out of the population).
After that allele is gone, gene pool gets smaller.
Two types of genetic drift
•bottleneck effect - occurs when a population is greatly reduced by events such as natural disaster or overhunting, resulting in certain alleles being overrepresented and other alleles being underrepresented or absent in the population, due to chance. Genetic variation in the surviving
population is reduced.
•Ex. Northern elephant seals. Overhunting. Surviving seals are protected, and increased in population again, but contain fewer variants in the alleles.
•Ex. Whooping cranes. 177 in Wood Buffalo National Park NWT thought to have come from 6-8 parents. Loss of diversity.
•founder effect (new species found) - cause of genetic drift due to a small group of individuals colonizing a new area. The small
group probably will not contain all the genes represented in the parent population.
•Ex. Hawaiian honeycreepers. Migrated from North America, inhabited several islands, and each population evolved into a different species, beginning with very few ‘parents’
•Ex. Human populations with founder effect have high incidence of genetic disorders. Newfoundland is an example of this.
•Ex. Small village in Venezuela has high incidence of Huntington’s.
3. gene flow - movement (or flow) of new genes into a gene pool.
This movement can reduce difference between populations that were caused by isolation and genetic drift.
•Ex. A windstorm or tornado can deliver new seeds to an area, resulting in new alleles into a gene pool if populations mix.
4. non random mating - Genetic equilibrium is maintained if there is no organized means to mate selection (completely random).
Often people in close proximity are more likely to mate than those more distant in a population (if one person moves away, the other is more likely to
find someone new who is still in the area).
•Inbreeding - mating between closely related partners. Results in a population with more homozygous individuals (mating between purebred dogs of same family).
•assortive mating - Individuals choose partners of similar phenotype (such as size). Ex. Many animals, like toads, choose a partner of similar size. This is the basis of artificial selection, and can result in decrease in genetic diversity.
5. natural selection - all animals are not equal in their ability to survive and reproduce. Some offspring leave more offspring than others.
There are selective pressures such as predation and competition, so those best suited to the environment are more likely to survive and reproduce, going against Hardy-Weinberg.
Three ways natural selection can affect the frequency of a heritable population:
stabilizing selection - natural selecton that favors intermediate phenotypes and acts against extreme variants (likes the
stable and predictable rather than the rebels ;) This reduces variation, as less are on the extremes.
•Ex. Babies born of “middle scale” weight are more likely to survive, than bigger or smaller babies. Over time, less and less bigger or smaller babies are born and more “middle of the road” babies are born (p. 693)
directional selection - favors the phenotypes at one extreme over the other, resulting in the distribution curve of phenotypes shifting in the direction of that extreme. This situation often occurs when there’s a time of environment change or species migrate to a new habitat (the most popular form moved in the direction of one of the extremes)
•Ex. Ancestral horses were smaller and had a forest habitat. When forests were replaced by grasslands, larger horses were more suitable for the environment based on durable teeth and longer legs for increased speed in the open area.
Other examples: the peppered moth, insect resistance to pesticides, bacterial resistance to antibiotics.
Disruption (diversifying) selection- opposite of stabilizing selection. When the extremes of phenotypes are favored rather than the
intermediate.
•Ex. Small salmon and large salmon are more likely to survive over medium sizedsalmon. Can eventually result in
only small and large salmon (no medium)
6. sexual selection. Selection for mating based on competition between males and choices made by
females.
•Ex. Plummage of peacock, fighting between males, Larger mane of a lion, bigger antlers of a moose. The ‘better’ male is more likely to be selected for sexual reproduction.
Objectives 18-20 – speciation p. 708-10, 716
Speciation – the formation of a species
Species – a population that can interbreed to produce viable, fertile offspring
Two pathways lead to speciation:
Transformation – process by which one species becomes a different species, as a result of accumulated changes over long periods of time. A.K.A. anagenesis
•New species gradually created while old species gradually lost
Divergence – one or more species arises from a parent species that continues to exist. A.k.a. cladogenesis
•Both arise by natural selection
•Speciation may occur due to: reproductive isolation, geographic isolation (rivers, canyons, mountains) see obj. 21
https://www.youtube.com/watch?v=rlfNvoyijmo: ~11 min
Obj. 21 – Biological Barriers that keep closely-related species separate. – p. 709-11
A. pre-zygotic barriers – barriers that prevent mating between species, or prevent fertilization of ova.
1. behavioural isolation– courtship ritual
–Phermones
–Bird songs
•Signals or behaviours that are species specific will prevent different species from mating
•Ex. Some birds that are closely related can identify their own species by their bird call.
2. habitat isolation – live in different habitats.
•Rarely encounter each other
•Ex. Common garter snake and northwest garter snake live in same area but northwes likes dry open areas where common snake is found mostly near water
3. temporal isolation – timing barriers
•Live in same habitat
•However, mate or flower at different times of day, different seasons, or years.
•Ex. Species of giant silkworm moths fly and mate at different times of day.
4. mechanical isolation – anatomically incompatible.
•Genitals don’t fit together
•Ex. Variations in flower structure
–Different arrangements of stamen and style
•Ex. Sage. One species needs to be pollinated by bees with pollen on their wings and another with pollen on
backs. A wrong visitor will not come in contact with stigma… no pollination.
5. gametric isolation – gamete won’t survive in the wrong environment –Ensures wrong gametes won’t fuse
•Ex. Chemicals from sea urchins will reject foreign sperm.
B. post-zygotic barriers – barriers that prevent a zygote containing gametes from two separate species from successfully developing into normal, fertile organisms.
1. hybrid inviability – genetic incompatibility stops development of zygote.
•Prevents normal mitosis after fusion of nuclei
•Ex. Combining sheep and goat gametes results in an embryo that will die in the early stages of development.
2. hybrid sterility – offspring is sterile.
•Can successfully mate two different species but offspring are sterile.
•Offspring doesn’t produce normal gametes .
•Ex. Horse + donkey = mule (sterile).
3. hybrid breakdown – offspring fine, but their offspring are not.
•F1 generation are viable and fertile
•Mating of the F1’s though have sterile or weak offspring.
•Ex. Cotton seeds from different species will produce fertile offspring, but the offspring of the F1’s will die as seeds or early in development.
Obj. 22 Adaptive Radiation p. 720
•Diversification of a common ancestral species into a variety of species, all of which are differently adapted.
•Ex. Finches of the Galapagos
•Birds from ancestral species were dispersed to the different islands.
•Islands were ecologically different enough to have different selective pressures
•Resulted in different feeding habits
•Gave rise to a variety of species with different adaptations.
•Another Example – Hawaiian Islands p. 691 –Honeycreeper - Came from ancestral finch
•Ex. Red crossbill in B.C. – size of bill determines size of cone eaten
-- These changes increase the possibilities for food supplies
Can occur in times after mass extinction, as environments and organisms present change.
Objective 23 – Convergent and divergent evolution
Divergent evolution – species that were once similar to an ancestral species diverge, or become increasingly distinct.
•Populations become less and less alike
•Eventually result in different species.
•Ex. Ancestral finch forms different species
Convergent evolution – similar traits arise in two unrelated species because each species has
independently adapted to similar environmental conditions, not because they
share an ancestor.
•Ex. Birds and bats
•Ex. Birds and bees
•Would explain why wings of each are so different
Speciation – the formation of a species
Species – a population that can interbreed to produce viable, fertile offspring
Two pathways lead to speciation:
Transformation – process by which one species becomes a different species, as a result of accumulated changes over long periods of time. A.K.A. anagenesis
•New species gradually created while old species gradually lost
Divergence – one or more species arises from a parent species that continues to exist. A.k.a. cladogenesis
•Both arise by natural selection
•Speciation may occur due to: reproductive isolation, geographic isolation (rivers, canyons, mountains) see obj. 21
https://www.youtube.com/watch?v=rlfNvoyijmo: ~11 min
Obj. 21 – Biological Barriers that keep closely-related species separate. – p. 709-11
A. pre-zygotic barriers – barriers that prevent mating between species, or prevent fertilization of ova.
1. behavioural isolation– courtship ritual
–Phermones
–Bird songs
•Signals or behaviours that are species specific will prevent different species from mating
•Ex. Some birds that are closely related can identify their own species by their bird call.
2. habitat isolation – live in different habitats.
•Rarely encounter each other
•Ex. Common garter snake and northwest garter snake live in same area but northwes likes dry open areas where common snake is found mostly near water
3. temporal isolation – timing barriers
•Live in same habitat
•However, mate or flower at different times of day, different seasons, or years.
•Ex. Species of giant silkworm moths fly and mate at different times of day.
4. mechanical isolation – anatomically incompatible.
•Genitals don’t fit together
•Ex. Variations in flower structure
–Different arrangements of stamen and style
•Ex. Sage. One species needs to be pollinated by bees with pollen on their wings and another with pollen on
backs. A wrong visitor will not come in contact with stigma… no pollination.
5. gametric isolation – gamete won’t survive in the wrong environment –Ensures wrong gametes won’t fuse
•Ex. Chemicals from sea urchins will reject foreign sperm.
B. post-zygotic barriers – barriers that prevent a zygote containing gametes from two separate species from successfully developing into normal, fertile organisms.
1. hybrid inviability – genetic incompatibility stops development of zygote.
•Prevents normal mitosis after fusion of nuclei
•Ex. Combining sheep and goat gametes results in an embryo that will die in the early stages of development.
2. hybrid sterility – offspring is sterile.
•Can successfully mate two different species but offspring are sterile.
•Offspring doesn’t produce normal gametes .
•Ex. Horse + donkey = mule (sterile).
3. hybrid breakdown – offspring fine, but their offspring are not.
•F1 generation are viable and fertile
•Mating of the F1’s though have sterile or weak offspring.
•Ex. Cotton seeds from different species will produce fertile offspring, but the offspring of the F1’s will die as seeds or early in development.
Obj. 22 Adaptive Radiation p. 720
•Diversification of a common ancestral species into a variety of species, all of which are differently adapted.
•Ex. Finches of the Galapagos
•Birds from ancestral species were dispersed to the different islands.
•Islands were ecologically different enough to have different selective pressures
•Resulted in different feeding habits
•Gave rise to a variety of species with different adaptations.
•Another Example – Hawaiian Islands p. 691 –Honeycreeper - Came from ancestral finch
•Ex. Red crossbill in B.C. – size of bill determines size of cone eaten
-- These changes increase the possibilities for food supplies
Can occur in times after mass extinction, as environments and organisms present change.
Objective 23 – Convergent and divergent evolution
Divergent evolution – species that were once similar to an ancestral species diverge, or become increasingly distinct.
•Populations become less and less alike
•Eventually result in different species.
•Ex. Ancestral finch forms different species
Convergent evolution – similar traits arise in two unrelated species because each species has
independently adapted to similar environmental conditions, not because they
share an ancestor.
•Ex. Birds and bats
•Ex. Birds and bees
•Would explain why wings of each are so different
Obj. 24. Coevolution p. 722
•Process in evolution where two species of organisms that are tightly linked (i.e., predator and prey) evolve together, each population responding to changes in the other population.
•Plants pollinated by birds –are red (to which insects are colorblind) and scentless (birds have poor sense of smell)
•Bacteria and antibiotics.
•Caribou and coyote. If all the weak, sick, slow caribou are caught, only faster, smarter, better camouflaged ones survive to reproduce.
•Process in evolution where two species of organisms that are tightly linked (i.e., predator and prey) evolve together, each population responding to changes in the other population.
•Plants pollinated by birds –are red (to which insects are colorblind) and scentless (birds have poor sense of smell)
•Bacteria and antibiotics.
•Caribou and coyote. If all the weak, sick, slow caribou are caught, only faster, smarter, better camouflaged ones survive to reproduce.
Objective
25
Gradualism - change occurs within a lineage, slowly and steadily, before and after a
divergence.
•big changes occur by the accumulation of many small changes.
•fossil record rarely reveals fossils that show this gradual transition
•generally find species appearing and disappearing suddenly
Gradualism - change occurs within a lineage, slowly and steadily, before and after a
divergence.
•big changes occur by the accumulation of many small changes.
•fossil record rarely reveals fossils that show this gradual transition
•generally find species appearing and disappearing suddenly
•Soooo...Elderidge and Gould developed the idea of
punctuated equilibrium - evolutionary history consists of long periods of equilibrium ‘punctuated’ or
interrupted by periods of divergence.
•most species undergo most change when they first diverge from parent species
•then very little change
•fossil record consists of fossils over long periods of time with little change and very few fossils in periods of rapid change.
Objective 26 - How did life begin in the First Place - Handed out in class - see file below:
punctuated equilibrium - evolutionary history consists of long periods of equilibrium ‘punctuated’ or
interrupted by periods of divergence.
•most species undergo most change when they first diverge from parent species
•then very little change
•fossil record consists of fossils over long periods of time with little change and very few fossils in periods of rapid change.
Objective 26 - How did life begin in the First Place - Handed out in class - see file below:
how_did_life_begin_in_the_first_place.doc | |
File Size: | 27 kb |
File Type: | doc |