1. Notepack # 42
Please write these notes on Loose Leaf. You will receive a 7 instead of a 5 for your inconvenience. Aim: Why do some organisms evolve faster than other organisms?
Do Now: Write down 2 differences between asexual and sexual reproduction.

2. What are the factors that drive evolution?
For evolution to occur many thing (factors) are needed to help force change within a population.
These factors are:
Variations
Reproduction
Environmental change

3. How does variation occur within a population?
For variations to occur, the organism’s genetic information (DNA) needs to be changed.
An organism’s DNA make up can change by the following:
Mutation
Recombination of chromosomes
Crossover of genes on chromosomes

4. Mutations
Mutations is a change of the nucleic base sequence of a DNA molecule.
This change causes the RNA to change.
If the RNA is changed, then the ribosome will get the wrong message and make a different protein.
The rate (speed) in which mutations occur is based on the type of organism and the environment the organism lives in.

5. Mutations (cont)
Mutations can occur naturally by exposure to sunlight, cosmic radiation, chemicals and food.
Mutation can also occur artificially by exposure to pollution and toxic chemicals.
If the mutation aids in the organism’s chances for survival the mutation is passed on to the next generation; if the mutations harms the organism’s chances to survive the mutation dies with the individual.

6. Recombination of Chromosomes
Recombination or recombining chromosomes occur during sexual reproduction.
When fertilization occurs, the zygote receives half of the chromosome from the mother and half of the chromosomes from the father.
Since the egg and the sperm are both made by meiosis, when the sex cell divides the new egg or sperm cell will randomly get chromosomes from either the grand mother and grandfather.

7. Recombination of ChromosomeD A B C D A B C D A B C D A B C D A B C D B C D A A B C D A D B C B C A D B C D A

8. Recombination of Chromosomes (cont)
Because there are so many different combinations of chromosome, each offspring will have a different combination of characteristics.
Some offspring will have a combination of traits that will help that individual to survive; while some combinations will hinder that organism’s chances of survival

9. Crossover of genes on chromosomes
During cell divisions chromosomes are duplicated.
When the chromosomes are line up in the middle of the cell during metaphase, some of the chromosomes rub next to each other.
During this “rubbing” some of the genes from one chromosome may cross over to the other chromosome and vice versa. This is known as crossing over.

11. Crossover of genes on chromosomes (cont)
Crossing over of genes between chromosomes changes the original chromosome into a chromosome that is slightly different.
A chromosome that was originally from the mother may now contain genes from the father.

12. Asexual and Sexual reproduction
Because of the mixing and recombination of chromosomes, sexual reproduction allows for more variations with in a population.
This means that some individuals in a population have a better chance of surviving if the environment suddenly changed.
Those that do survive will pass on their genes to the next generation therefore evolving the population.
Asexual reproduction produces clones therefore each individual is identical to each other. That means what kills one will kill the other

13. No Variation

14. With Variation

15. Mutating Bacteria and Antibiotic
Bacteria are micro-organism that live almost everywhere.
When your are sick because of a bacteria, you take an antibiotic. (kills bacteria)
Because of mutations and chromosome crossovers some bacteria are resistant (won’t die) to the antibiotic and survive to reproduce.
As the normal bacteria dies, the mutated bacteria continues to reproduce there by changing the population.
The new population is now resistant to the antibiotic, so doctors must prescribe a new type of antibiotic to kill the mutated bacteria.