Evolution Standard BL7

1. Evolution Standard BL7

2. Evolution Standard BL7 BI7. The frequency of an allele in a gene pool of a population depends on many factors and may be stable or unstable over time. As a basis for understanding this concept, students should know: Example #1: Rabbits in a field are mostly a brownish-gray color (full color) and tend to blend in well with their surrounding habitat. Rabbits which are lighter or even white in color, tend to be easier prey for predators such as hawks and coyotes. This means the gene pool of all the full color rabbits are more likely to survive and be passed down to the next generation and those of the lighter colors, will be reduced due to natural selection. Full color Albino

3. Evolution Standard BL7 BI7. a.why natural selection acts on the phenotype rather than the genotype of an organism. The color of the rabbit in the pervious is the phenotype and the genotype is what makes it white or full colored. White rabbits still show up when the genotype allows it, thus proving it is the phenotype that is affected. Which one would you “see”? Example #1: Phenotype is the physical characteristic of an organism, such as color, size, or the unnoticed trait which may or may not effect the organisms survival. Genotype on the other hand, is the genetic material which causes the phenotype. The “genes” if you will! Phenotype Genotype

4. Evolution Standard BL7 BI67 b.know why alleles that are lethal in a homozygous individual may be carried in a heterozygote and thus maintained in a gene pool. Example #1: Cystic fibrosis (also known as CF or mucoviscidosis) is an autosomal genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine. Here the “Carrier” father Rr is heterozygous as is the “Carrier” mother. Their children may be; HomozygousRR and a non-carrier (25%) ; Heterozygous Rr (50%) unaffected like parents; or Homozygous rr(25%) for the lethal (recessive) CF and will die! Therefore as long as there are heterozygous parents, there is the chance of passing on the lethal gene to future generations.

5. Evolution Standard BL7 BI7. c.students know new mutations are constantly being generated in a gene pool. Example #1: As humans breed cats, mutations appear. These mutations produce different genotypes for say, tail shape, different tails shape phenotypes also appear. When a mutation posses no threat to the survival of the species, then the alleles which caused the mutation can increase in the gene pool and appear more and more. Common cat tail shapes caused by mutations at one time during naturallybreeding processes or through human selective breeding processes.

6. Evolution Standard BL7 BI7. d.variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions. Example #1: if we only ate one species of plants, say a rice, then we would die if that species of rice fell prey to a disease or parasite and wiped it out. Because of biodiversity, or variety, we have not only a choice of foods, but back ups in case one dies off.

7. Evolution Standard BL8 BI8Evolution is the result of genetic changes that occur in constantly changing environments. As a basis for understanding this concept, students should know; Example #1: As environmental ecosystems change, so do the survival of the species living there. In England a moth, called the pepper moth, lived in and around the country side. The moth is and was white with black spots. As the Industrial Revolutions hit Europe, large factories bellowed out large amounts of smoke and soot which covered much of the vegetation and rocks where the pepper moth lived. Over time, mutations in the moth allowed a darker version to have better survival rates. Eventually, two different species of pepper moth formed, one light colored and one dark colored. These two species no longer breed together and have become behaviorally isolated.

8. Evolution Standard BL8 BI8. a.how natural selection determines the differential survival of groups of organisms. Example #1: natural selection is the way most organisms survive and live. They are either eaten or are the eaters. Predator/Prey relationships are all around us. Only those at the top of the food web do not normally have natural predators. Small fish are eaten by larger fish, which in turn are eaten by even larger fish. Any genetic change which benefits the survival chances of a species allows those alleles and genes to be passed down from generation to generation, continually increasing the survival of the fittest.

9. Evolution Standard BL8 BI8. b.a great diversity of species increases the chance that at least some organisms survive major changes in the environment. Example #1: If a lake had only one type of fish and that fish ate only one type of aquatic insect as food, any change in the population of the insect could cause disaster for the fish. Salmon Fly Brown Trout By having a variety of foods to feed on, other insects and small fish, to mice and terrestrial insects like grasshoppers, the trout can feed on many food sources. The loss of one, may not cause the trout to die off.

10. Evolution Standard BL8 BI8. b.a great diversity of species increases the chance that at least some organisms survive major changes in the environment. Will you survive? Example #2: If another asteroid should happen to hit Earth, the wide variety of plants and animals, among other organisms, increases the chances of at least some of these organisms will be able to survive and later flourish in what will certainly be a “new” environment.

11. Evolution Standard BL8 BI8. c.the effects of genetic drift on the diversity of organisms in a population. Example #1: When a small population has part of its gene pool removed, the diversity of the remaining members has also be reduce. This reduction in the gene pool from genetic drift is usually due to some short term change or small sub-population emigration out of the original population. The gene pool that remains, often has a smaller biodiversity and therefore some phenotypes, along with their genotypes, may disappear from the original population.

12. Evolution Standard BL8 BI8. c.the effects of genetic drift on the diversity of organisms in a population. Example #2: A house becomes infested with cockroaches. When a pesticide is sprayed on them, not all of the roaches are killed. Those that survive may be resistant to the pesticide used. They then pass this resistance on to their offspring and these new populations also are resistance. In the end, we may have created a species of cockroach which can not be killed with pesticides!

13. Evolution Standard BL8 BI8. d.reproductive or geographic isolations affects speciation. Example #1: When two groups of the same species become separated by some large geographic barrier such as a ocean, large mountain range or large river, they become geographically isolated and speciation, the forming of a new species, occurs. This is a green iguana and lives in the forest of South America. It is believed to be related to the marine iguana which inhabits the Galapagos Islands 600 + miles off the coast of So. Am. Although related, these are considered two different species because they no longer breed with each other.

14. Evolution Standard BL8 BI8. d.reproductive or geographic isolations affects speciation. Example #1: When two groups of the same species breed at different times of the year, or even day, this is an example of reproductive isolation. Here the two species could still breed, but because they do not, they have isolated their gene pools and separated as species. Below are two different King Salmon. One spawns in the spring and one in the fall. They could still reproduce, but the different times have separated the gene pool of these two, thereby isolated and have adapted to different water temperatures and flow rates. Also called Temporal Isolation. Spring King Fall King

15. Evolution Standard BL8 BI8. e.how to analyze fossil evidence with regard to biological diversity, episodic speciation, and mass extinction. Example #1: The wide variety of fossils found over the years shows that the Worlds organisms have changed and were at time much different. However, scientists can use information regarding these fossils to make assumptions and theories about present day organisms. For example, the two species below are most likely related. One being millions of years old and sometimes many times larger than the current species.

16. Evolution Standard BL8 BI8. e.how to analyze fossil evidence with regard to biological diversity, episodic speciation, and mass extinction. Example #2: Because we no longer have dinosaurs roaming the Earth, the fossil record of these creatures shows that for some period of time, these organisms lived and even thrived, yet some factor caused a mass extinction of these reptiles and many other organisms. This pattern of evolutionary growth and developed, called episodic speciation, is often followed by some mass extinction and has been shown to have occurred several times in the history of the World.

17. Evolution Summary • Charles Darwin was given credit for the Theory of Evolution. He and others paved the way for thoughts of changes in our world over time. This change is caused by many different things, some environmental, some genetic. Some changes help the survival of organisms and some harm them. Those which make the organisms better able to survive, will also allow them to pass those traits on to their offspring. • From time to time, some large scale event causes a large amount of species to be lost all about the same time. These mass extinctions allow other species to flourish and fill in niches which were used be previous species. • Species change as does the environment. Evidence of this change can be seen many places and includes; fossil records, extinctions, coevolution, convergentevolution, and adaptive radiation. These are the tools and resources scientists use to try and find out about our past world. • Evolution is an on going processes which often takes thousand or even millions of years. By having these changes occur, the Earth has a great biodiversity which allows many species to form and be lost, without being void of all life on our planet.

18. Evolution Summary • The History of Earth’s organisms began some 650 million years ago, but only recently have human’s appeared. Below are some of the fossil remains of our ancestors and the changes they seemed to have gone though to get us to where we are. Changes which are still occurring; 14 changes over the last 1.8 millions years! Earliest Most Recent