What Can Cause a Change in Allele Frequency?
1. Mutation: A mutation is a change in a DNA sequence. Mutations can be caused by a mistake in cell division, exposure to radiation and chemicals, and infection by a virus. However, mutation MUST occur in the egg or sperm to be passed down to offspring; it cannot occur in body cells where it is not passed down. Across is a diagram of mutation, it shows the different forms of mutations and how the affect a DNA sequence.
2. Migration: Migration is the transfer of genes/alleles from one population to another. Genes are carried from one population to another population where the genes did not previously exist. Across is a diagram of migration, notice how the brown bug is moving to the green bug population. 3. Genetic Drift: Allele frequency changes based off of who is the "luckiest" individual, not the "better" individual. Whichever animal is the luckiest, such as who survives a natural disaster, is the one who will live and pass down there genes. Across is a diagram of genetic drift, notice how the green bugs die out not because they are better, but they just happened to be the ones stepped on. |
Natural Selection: How it Works and the 3 Types of Selection
Natural selection is often described as the "survival of the fittest." It is when a trait becomes more or less common to better adapt to its environment. Natural selection begins with genetic variation, but something in the environment does not support one version of the gene. Therefore, the advantageous version of the trait is more successfully reproductive. For example, there are brown and white moths in an area. The trees are brown, therefore the brown moths camouflage and the white do not, making them easier to be seen by predators. The white are eaten, therefore they cannot reproduce, whereas the brown survive and can reproduce. There are three types of selection: stabilizing selection, directional selection, and disruptive selection. Stabilizing selection is when the medium of a trait is supported, and the extremes are not (example: claw length and traction; medium length claw the best). Directional selection is when one extreme is supported by the environment (example: amount of body fat in the Arctic; high amount of body fat equals more warmth). Disruptive selection is when both extremes are supported (example: black and white fur and the presence of black and white rocks to camouflage).
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Evidence of Evolution
One evidence of evolution are homologous structures. These are when different species have similar structures, such as limbs. This proves that different species can share a common ancestor, but variation of the limb shows how the organism has adapted to its environment.This is similar to divergent evolution, which is the adaptations of similar species to different environments. Vestigial organs are structures that were once used but know longer serve a purpose fro the organism, but they are still there. The presence of vestigial organisms helps to show that animals once had a purpose for these organs, but later adapted to their environment more efficiently and no longer used them. Convergent evolution is unrelated species showing similar characteristics because of similar environments. Similar to the other presented evidence, this helps to prove how organisms have adapted to the environments. Embryology is also evidence of evolution. At first, all embryos look similar, all having a tail and gills. Over time as the embryo develops, it loses or keeps the tail and gill , depending on what animal it is, and develops whatever body parts necessary uniquely to that organism. This shows how animals have evolved to develop what they need for their environment and lifestyle. It is also proof that we share a common ancestor. Fossils are a major evidence of evolution. Remains of ancient plants and animals found in sedimentary rock can help to track how animals have changed over time, and we can predict the age of the fossils by measuring how deep the fossil is in the sedimentary rock. This process is called relative dating. Geography can also help to prove evolution. The same species found on a continent, such as Africa, was also found on another, such as South America. This also proves we have a common ancestor and the similarity of the animals found on both continents shows they are adapted to their environments.
Special Adaptations of the Nine Banded Armadillo!
1. The nine banded armadillo has strong body armor made up of horn and bone which significantly helps them be protected against predators.
2. Their brownish-green color assists in camouflage with their scrubby grassland habitat. 3. When chased by a predator into a burrow, the armadillo can wedge itself into the tunnel with its back to the outside. This makes it almost impossible to dislodge. [1] 4. " In order to cross deeper or wider waterways, the armadillo can swim across much like a dog. It is able to do this thanks to its ability to gulp air and inflate its digestive tract." [2] It can hold its breath for six minutes or more! 5. The nine banded armadillo can jump three to four feet in the air when startled, which may help to scare away predators. 6. Nine banded armadillos have very long, sticky tongues that can be used to forge for insects in the dirt. |
Evolution of the Armadillo
The earliest ancestor recorded of the armadillo is the Glyptodon and Panocthus. These animals were very large, and have an armored shell. They closely resemble the modern day armadillo, except much larger.