Evolution is change over time. Organisms adapt to survive the best they can in their environment. One way that they do this is by changing their allele frequency and passing it on to their offspring. Alleles are versions of a trait. There are four different factors that cause a change in allele frequency.
The first way in which allele frequency can change is through mutation. Mutation is when the nucleotide sequence of an organism changes. Nucleotides are what make up nucleic acids such as DNA and RNA. Mutation can be harmful or helpful. It sometimes prevents genes from working correctly or affects reproductive success. It can also just have no affect on the organism. Mutations are also sometimes unable to be passed on. This is called somatic mutation and only affects the appearance of affect the organism's body and can't be passed n.
Another way allele frequency can change is by genetic drift. It's a random, typically occurring in small populations due to random sampling. This happened with the Amish population. They interbred with one another so that there wasn't a lot of variation and everyone has many of the same traits. In the Amish populations, that was a syndrome where they have six fingers.
Migration is when a group of individuals move from one population to another. Genes are shared between the population that currently lives in the place where the new group is coming to. This increases genetic variation. For example, this could happen with bugs (show in picture on right).
The final way allele frequency changes in natural selection. It's survival of the fittest. The organisms that are the fittest to live in certain places, that have the correct genes that help them out, are the most reproductivly successful. There are more of them that survive, so more of them are able to reproduce, causing a large number of offspring. For example, with bird beaks, the bird with the beak most suitable for eating will be the most successful because it will get the most food and therefore live longer and produce more children.
There are three types of natural selection. The first type is stabilizing selection. This is where the environment supports the medium. An example is birth weight. Light babies are able to lose heat quickly and may not survive. Large babies are difficult for the mother to give birth to and may harm her. The middle weight is supported. The second type is directional selection where the environment supports either extreme. In London during the Industrial Revolution, this happened with moths. Trees were turning black from coal so the white moths were dying off because they couldn't camouflage themselves with the trees. The black moths survived because they were able to blend in and the black extreme was supported. Disruptive selection is when the environment supports both extremes. An example is in mice. Both black and white mice are supported by the environment but the middle (grey) isn't. Black mice blend in with the shadows and white mice blend in with brightness, but grey mice don't blend in very well anywhere.
Indian Red Scorpion Special Adaptations:
They're red, orange, brown and grey in order to blend into their surroundings
Scorpions have a very slow metabolism that allows them to to survive even when food is scarce. Some are capable of living for up to a year without food or water.
Scorpions can survive in very tough environment and some are able to freeze overnight and thaw out in the morning
Scorpions glow in the dark. Scientist aren't sure why they do this but some ideas are that they do it to dazzle prey or it acts as a kind of sunscreen for their sensitive skin.
Scorpions shed their exoskeleton.
Scorpions have changed very slightly since the Silurian Period. However, they are believed to be descendants of lobsters. It is believed that they used to have gills and were the first animals to adapt from living in the water to living on land. A 505 million year old fossil was recently found called Kootenichela deppi. It's an ancestor of scorpions and lobsters.