The Basics of Evolution
Evolution - is a widely accepted theory which suggests how different species of living organisms have developed and diversified from the early simplistic creatures to complex organisms. Over time the allele frequency changes. Allele or gene frequency is the percentage of all alleles in a given population. There are four ways allele frequency can change over time: mutation, migration, genetic drift, and natural selection.
1) Mutation
Mutations are the only way new alleles can be created. Mutations can either improve the organism and help the species' chance for survival or harm it. Mutations may or not affect the reproductive success of a species. Reproductive success is being able to pass on genes that the next generation can also pass on those genes. An example of a mutation that did not affect reproductive success positively or negatively is blue eyes in humans. The only way a mutation can be heritable, meaning it's able to be passed on to the next generation, the gametes have to carry the mutation.
2) Genetic Drift
Genetic drift is a random change in allele frequency. Two examples of genetic drift is the founder effect and the population bottleneck. The founder effect is when a random sample of genes is placed into a new population and that seemly random or rare trait becomes dominant in the new population. For example in a small omish town the common trait is that people have six fingers. Population bottleneck is when an environmental event causes a drastic decrease in a population. A random allele that might have been rare in the population suddenly becomes common.
3) Migration
Migration, otherwise known as gene flow, is when a group of individuals moves from one population to another which can change the allele frequency.
4) Natural Selection
The term "survival of the fittest" describes natural selection. Natural selection is when those best suited to their environment, survive and reproduce. There are three conditions needed for natural selection to occur:
1. Stabilizing Selection
-stabilizing selection is when the environment supports the medium
For example if the original population of plants was very short, medium height and very tall, stabilizing selection would create an environment with mostly medium sized plants.
2. Directional Selection
-the environment supports either extreme
For example the plant environment would then have either mostly tall plants, or mostly small plants.
3. Disruptive Selection
-the environment supports both extremes
For example the plant environment would have mostly tall and short plants and very few medium.
1) Mutation
Mutations are the only way new alleles can be created. Mutations can either improve the organism and help the species' chance for survival or harm it. Mutations may or not affect the reproductive success of a species. Reproductive success is being able to pass on genes that the next generation can also pass on those genes. An example of a mutation that did not affect reproductive success positively or negatively is blue eyes in humans. The only way a mutation can be heritable, meaning it's able to be passed on to the next generation, the gametes have to carry the mutation.
2) Genetic Drift
Genetic drift is a random change in allele frequency. Two examples of genetic drift is the founder effect and the population bottleneck. The founder effect is when a random sample of genes is placed into a new population and that seemly random or rare trait becomes dominant in the new population. For example in a small omish town the common trait is that people have six fingers. Population bottleneck is when an environmental event causes a drastic decrease in a population. A random allele that might have been rare in the population suddenly becomes common.
3) Migration
Migration, otherwise known as gene flow, is when a group of individuals moves from one population to another which can change the allele frequency.
4) Natural Selection
The term "survival of the fittest" describes natural selection. Natural selection is when those best suited to their environment, survive and reproduce. There are three conditions needed for natural selection to occur:
- variation in a trait ex) running speed in rabbits can vary from one individual to the next
- the trait must be heritable ex) the trait of running speed is passed on from parents to their offspring
- differential reproductive success ex) in a population rabbits with slower running speeds are eaten by the fox and their traits are not passed on to the next generation
1. Stabilizing Selection
-stabilizing selection is when the environment supports the medium
For example if the original population of plants was very short, medium height and very tall, stabilizing selection would create an environment with mostly medium sized plants.
2. Directional Selection
-the environment supports either extreme
For example the plant environment would then have either mostly tall plants, or mostly small plants.
3. Disruptive Selection
-the environment supports both extremes
For example the plant environment would have mostly tall and short plants and very few medium.
Evidence of Evolution
1) Fossil Record
The first piece of evidence that supports the theory of evolution is fossil records. Fossils can show how species changed over time and how they are related to creatures that died millions of years ago. Relative dating is what is shown in the diagram. A scientist can tell which fossil is older based on how deep it is. Radio metric dating uses radio waves to find exactly how old a fossil is.
2) Geography and Species
Some of the same fossils have been found on different continents. This shows that these species had a common ancestor and a similar environment from which the evolved from.
3) Comparative Anatomy
5) Field Studies- putting different environmental stresses on a species causes it to evolve into a different species
The first piece of evidence that supports the theory of evolution is fossil records. Fossils can show how species changed over time and how they are related to creatures that died millions of years ago. Relative dating is what is shown in the diagram. A scientist can tell which fossil is older based on how deep it is. Radio metric dating uses radio waves to find exactly how old a fossil is.
2) Geography and Species
Some of the same fossils have been found on different continents. This shows that these species had a common ancestor and a similar environment from which the evolved from.
3) Comparative Anatomy
- Homologous Structures- different species have similar bone structures ex) whales and primates both have fingers but whales have evolved to have fins covering those fingers
- Vestigial Organs- structure that were once used but no longer have a purpose ex) humans no longer use our appendix and tail bone
- Divergent Evolution- the adaptation of similar species to different environments creating a new species ex) the same species of finches went to different islands with different environments and developed different adaptations
- Convergent Evolution- unrelated species show similar characteristics because of their similar environments ex) both orcas and penguins both have pelagic coloring, meaning that the top of them are dark and the bottom are white so they are able to blend in if something was looking up or down at them
- Embryology- the similarity between the embryos of different species ex) pig, fish, and human and human embryos each have a tail and a gill like structures
5) Field Studies- putting different environmental stresses on a species causes it to evolve into a different species
The Evolution of Birds
Scientists believe that birds began evolving in the Jurassic period and stem from a group of dinosaurs called Paraves, which is where the class name for birds comes from: aves. Aves are defined as ancestors of the most common modern bird species (ex. House Sparrow) and some prehistoric, early bird species.The earliest known bird is called Archaeopteryx lithographica. It had feathers on its arms and tail, like modern birds, but also had sharp teeth, and a long bony tail. Over time the shoulder girdles, pelvis, and feet bones of the earliest bird have fused in modern birds. [1]
Special Adaptations:
1. The Great Blue Heron has especially long legs to help it hunt in deeper water.
2. The Great Blue Heron has a special vertebrae in its neck that allows it to curve into an "S" shape. This allows the neck to strike it's prey at lighting fast speeds. When the birds fly the next folds back for better aerodynamics.
3. Great Blues have a special powder in their down feathers, which they shake off and onto fish. The powder slime and oil to clump up on the fish so that the herons can easily wipe it off. Herons also rub the powder on the belly of the fish to get rid of swamp slime and oils.
4. Herons can swallow fish much larger then their narrow necks
5. Over time the skull bones of birds have fused to create a skull with better aerodynamics
6. A key evolutionary step for birds is when they adapted to have hallow bones. This made flight much more possible
7. Unlike most birds herons do not have crops or gizzards to grind up their food, but since they swallow their prey whole they have especially tough stomachs and strong stomach acids
8. Over time the pelvis, hands and feet of birds have fused to create slimmer and more aerodynamic bodies
9. Birds have evolved to have no teeth
10. Over time the ribs of birds have strengthened
11. Birds have developed extraordinary song and communication abilities
12. Each part of the jaw became covered in an outer shell to become the beak
13. Birds do not have sweat glands
14. Birds have a four- chambered hearts and very high metabolic rates to support the amount calories and energy burned during flight
15. Birds have a fully ossified skeleton with air cavities.
1. The Great Blue Heron has especially long legs to help it hunt in deeper water.
2. The Great Blue Heron has a special vertebrae in its neck that allows it to curve into an "S" shape. This allows the neck to strike it's prey at lighting fast speeds. When the birds fly the next folds back for better aerodynamics.
3. Great Blues have a special powder in their down feathers, which they shake off and onto fish. The powder slime and oil to clump up on the fish so that the herons can easily wipe it off. Herons also rub the powder on the belly of the fish to get rid of swamp slime and oils.
4. Herons can swallow fish much larger then their narrow necks
5. Over time the skull bones of birds have fused to create a skull with better aerodynamics
6. A key evolutionary step for birds is when they adapted to have hallow bones. This made flight much more possible
7. Unlike most birds herons do not have crops or gizzards to grind up their food, but since they swallow their prey whole they have especially tough stomachs and strong stomach acids
8. Over time the pelvis, hands and feet of birds have fused to create slimmer and more aerodynamic bodies
9. Birds have evolved to have no teeth
10. Over time the ribs of birds have strengthened
11. Birds have developed extraordinary song and communication abilities
12. Each part of the jaw became covered in an outer shell to become the beak
13. Birds do not have sweat glands
14. Birds have a four- chambered hearts and very high metabolic rates to support the amount calories and energy burned during flight
15. Birds have a fully ossified skeleton with air cavities.