Who Survives?

Insect larvae

NATURAL SELECTION: Organisms that are better equipped for their environment have a greater probability of surviving and passing on their genetic information.

Four (4) MECHANISMS of Natural Selection Overproduction: This refers to organisms producing more offspring than can survive. 2. Genetic Variation:  members of a species differ from one another with regard to inherited traits. Differences between individuals within the same species is called VARIATION.

3. Competition: Food, mates, space, water…limiting factors…remember 3. Competition: Food, mates, space, water…limiting factors…remember? Offspring compete for these resources…sometime directly…sometimes indirectly. 4. Selection (Successful Reproduction):  Some variations make certain individuals better adapted to compete in their environment. Those individuals are more likely to survive and reproduce.

After many generations, more organisms within the species are likely to have a beneficial trait. It accumulates (builds up). Over a long period of time, natural selection can lead to evolution. How? Beneficial variations gradually build up within a species, while unfavorable ones disappear. This lab will demonstrate how this happens.

Whatz Up Scenario One of the hottest new pets on the market is furless bunnies. Your friend, who lives in England (why not?), has a thriving business breeding furless bunnies., one day he comes home to find all of his furless bunnies have escaped into the forest next to his home… Tragic

He is having a very hard time catching his bunnies He is having a very hard time catching his bunnies. He is concerned that his furless bunnies will not survive the harsh winter and that the large population of furred bunnies in the forest will breed with his bunnies.

He has called on you (what is he thinking) to help him determine what will happen to his population of furless bunnies if they were to remain in the wild. You (sciency individual that you are) will examine how natural selection will affect the genotypes of phenotypes of the bunny population.

Instructions (record this information on your data sheet please) Problem: How might natural selection affect the bunny population over several generations? Hypothesis: ____(Write your hypothesis here)________________________________________________________________________________________________________________________________________________

Collect materials: bag with 20 red beans, 20 white beans, one cup. -Red beans represent the allele for fur -White beans represent the allele for no fur. -The container represents the deciduous forest ecosystem, where the rabbits mate randomly. 2. Draw beans two at a time and tally as we will discuss. FF=Fur=2 red beans together Ff=Fur=1 red and 1 white together ff= Furless=2 white beans together 3. Remove the ff’s (two white drawn together) from the population. They did not survive. 4. All other beans go back in the cup…draw the next generation. Repeat #2 and #3 for ten (10) generations.

5. Without looking at the beans, select two at a time, and record the results on the data form next to "Generation 1." For instance, if you draw one red and one white bean, place a mark in the chart under "Number of Ff individuals." Continue drawing pairs of beans and recording the results in your chart until all beans have been selected and sorted. Place the "rabbits" into the appropriate dish: FF, Ff, or ff.

6. The ff bunnies are born furless (yecchhh. ) 6. The ff bunnies are born furless (yecchhh!). The cold weather kills them before they reach reproductive age (sooo sad ), so they cannot pass on their genes…DEAD BUNNIES! To represent the death of the naked bunnies, place the beans from the ff container aside before beginning the next round.

7. Place the alleles of the surviving rabbits (which have grown, survived and reached reproductive age) back into the container and mate them again to get the next generation. 8. Repeat steps five through nine obtain generations two through ten. If working as a team, make sure everyone in has a chance to either select the beans or record the results. 9. Once you have determined the genotypes of each generation, calculate the phenotypes. 10. Graph your data.

how common the allele is compared to others. Gene Frequency What is Gene Frequency? It’s the frequency of occurrence of an allele in relation to that of other alleles of the same gene in a population…or… how common the allele is compared to others.

How to Determine Gene Frequency: Fq F = F/( F + f) Fq f = f/( F + f) In words that is… To find the gene frequency of F (the dominant trait…fur), divide the number of F‘s by the total number of alleles (F’s plus f’s). Do the same thing for f (the recessive trait…furless). You will get answers in decimals. Adding the two gene frequency numbers together should equal 1… Fq F+Fq f=1.0