Cross+Talk!



= = =This page is called CROSS TALK. . . want to work with the other AP class Mr. Beal has. . . this is your chance!!!= ​

= Evidence for Evolution = Hello students! This is our first attempt at using lap tops and the Wiki in class. Fingers crossed. . .Chapter 22, in our text book, deals with EVIDENCE for EVOLUTION. Instead of having Mr. Beal drone on and on. . . I've decided to let you do some digging.BOTH AP classes will work on the following. Mr. Beal has 13 total lab groups and each will only get one topic!Assignment: The following evidence supports evolution

=**1. Darwin's Finches**=


 * On Darwin's trip to the Galapagos Islands he encountered finches on each island that were so different from each other that they were almost different species. These different birds were unique to each island and are examples of how natural selection works. Each bird's beak is based off what food is available on their island. [[image:birds.jpg width="467" height="393"]][[image:chart.jpg width="302" height="338"]][]**

=**2. Variation**=

The extent to which the characteristics of the individuals of species can vary. Variation can be caused by environmental and genetic factors. Environmental variation results in differences in the appearance of individuals of a species because of differences in nutrition, disease, light intensity, etc. Genetic variation is caused by recombinatin and occasionally by mutation. These differences may be favored or discriminated against by natural selection. Without genetic variation, some of the basic mechanisms of evolutionary change cannot operate.There are three primary sources of genetic variation, which we will learn more about: Genetic shuffling is a source of variation.
 * 1) **Mutations** are changes in the DNA. A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations.
 * 2) **Gene flow** is any movement of genes from one population to another and is an important source of genetic variation.
 * 3) **Sex** can introduce new gene combinations into a population. This genetic shuffling is another important source of genetic variation.

=**3. Over production and competition**=

Production & Competition [|**http://answers.yahoo.com/question/index?qid=20080409181748AAAjEo0**]
 * Competition
 * Definition:
 * Sociology
 * rivalry between two or more persons or groups for an object desired in common, usually resulting in a victor and a loser but not necessarily involving the destruction of the latter
 * Ecology
 * the struggle among organisms, both of the same and of different species, for food, space, and other vital requirements
 * This interaction is detrimental to both species involved
 * Examples
 * Weeds in a garden compete for soil nutrients and water with garden plants
 * Lynx and foxes compete for prey like hares
 * Results
 * Reduction in the density of one or both species
 * Local elimination of one of the two competitors
 * Evidence for Evolution
 * Organisms evolve to stay alive, referring back to survival of the fittest. They adapt in order to stay alive and overcome competition.
 * Overproduction
 * Definition
 * excessive production; production in excess of need or stipulated amount
 * the process of producing far more offspring than will survive to produce offspring of their own
 * This interaction will be beneficial to the new organisms (life), and detrimental to population for having an excessive amount of organisms
 * Examples
 * A population of groundhogs reproduced, quadruples its population, and within 4 months completely wiped out its food supply, causing migration and extinction.
 * Results
 * Migration
 * Death
 * Extinction
 * Evidence for Evolution
 * Organisms adapt in order to still be able to reproduce and stay alive. Over generations, organisms learn how to reproduce in a way that allows them to live comfortably. This might mean migration and limiting reproduction values.

=**4. Survival of the fittest**=

**Survival of the fittest**: Those with the traits that fit the environment will survive. When the environment changes, those who are fittest to the new environment will survive and the others will perish. **Giraffes with long and short necks proving Darwin' s Theory of Evolution **

=**5. Fossils **=



Fossil species appear and disappear throughout the stratigraphic record. The Geologic Time Scale is based on these appearances and disappearances. Each of the Eras ends with a mass extinction. Period boundaries coincide with smaller extinction events, followed by appearances of new species. [|**http://www.bbc.co.uk/sn/prehistoric_life/dinosaurs/making_fossils/**] <== Open the flash animation and watch the process bodies must go through to become fossils

=**6. Analogous Structures**=
 * [|Analogous structure]s are features of different [|species] that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature.
 * Part of convergent evolution (The evolution of species from different taxonomic groups toward a similar form; the development of similar characteristics by taxonomically different organisms)
 * These similar strucures are created so an organism can adapt to their environment
 * An example of an analogous structure would be the wings of a bird and the wings of an insect. Both originate separately, but are used for the same purpose: to fly.
 * Another example is the arm of a human and the arm of a crab. Crabs use their arms and claw to pick up objects. Humans use their arms and hands to do the same function as well.



=**7. Homologous Structures**=
 * Darwin's concept of "homology" explains that similarities in structures of species is a result of a common ancestor
 * the forelimbs of all mammals show the same arrangement of bones from the shoulder to the tip of the digits
 * the resemblances between species would not exist if the structures had came from new individual species
 * homologous structures: structures in different species that are similar because of common ancestry
 * in the early stages of animal development (embryos) there are structural similarities that are not found in the adult form of the organism
 * evolution only modifies existing structures and functions

> > =__8. Vestigial Organs__=
 * Organ that is functionless and generally reduced in size but bears some resemblance to the corresponding fully functioning organs found in related organisms
 * Organs or organ structures remaining or surviving in a degenerate or imperfect condition or form
 * Examples are wings of flightless birds, the appendix and ear muscles of humans, the pelvic bone of a whale, and the limb girdles of snakes
 * These organs are evidence of evolution, which because of gradual changes in the environment or lifestyle, caused the function to become nonexistent
 * Relate how species are related to one another through ancestors

=9. Comparative Embryology=

Comparative EmbryoloComparative embryology is the comparison of different animals in various stages of embryonic development.comparative biology has proven, as you can see in the image, that many animal species, including humans, look very similar in our early and middle stages of embryonic development. Biologists have theorized that this is due tour relation to a common ancestor.

=10. Molecular Biology= Princeton defines molecular biology as: the branch of biology that studies the structure and activity of macromolecules essential to life (and especially with their genetic role)The DNA and proteins in many species are very similar to each other. The amino acid sequence of the hemoglobin in humans and other vertebrates is very similar. For example, gorillas only have one amino acid difference out of 146 amino acids compared to humans (99% similar). Even frogs have a 54% similarity to humans; only 67 per set of 146 amino acids are different.

=11. Artificial Selection=



Artificial selection, occasionally referred to as selective breeding, is when people only allow animals with desirable traits to reproduce. []

12. Natural Selection



Selection is the differential success in reproduction among species that vary in their heritable traits. These reproductive differences emerge as each individual interacts with its environment.A study was done by John Endler of University of California, Santa Barbra, and David Reznick of University of California, Riverside conducted a study to prove natural selection. They studied an environment of guppy populations in pools in the Aripo River system in Trinidad. Two pools were evaluated and each had a predator that preyed on guppies at different sizes. Depending on the predator the guppies grew at a slower or faster rate at which they matured sexually.The process of Natural Selection is a long process that will adapt a species to its environment to be able to reproduce and thrive without the threat from different variables surrounding it. The process of Natural Selection leads to Evolutionary Adaption, which is the gathering of inherited traits that enhance species ability to survive and reproduce in specific environments.

=13. Biogeography=

Darwin's observations of the geographic distribution of species-known as bio-geography formed an important part of his theory of evolution. Closely related species tend to be found in the same geographic region, whereas the same ecological niches in distant regions are occupied by very different species.These different species look similar but, since they are from different parts of the world, they aren't closely related. They evolved similarly in order to better surviveCreate on this page a visual representation of your topic. Use definitions, videos, animations, interviews, anything on the web, etc. . that will CORRECTLY convey your evidence for evolution! This is a two day in class assignment and over the weekend if needed!Good luck!