1. HOW ARE TRAITS PASSED ON?

2. How does natural selection change a species?
Factors in nature (climate, resources, competition, etc) favor the traits that are most adapted for survival
Organisms with the best traits to fit the environment survive and reproduce while those with traits that aren’t well adapted die and are unable to pass on their traits
This is called survival of the fittest
Bad traits are eliminated and good traits go to the next generation
Over long periods of time, as the environment constantly changes, the best traits will vary and eventually you can have an organism that looks very different from its ancestor

3. So why were there so many different species of finches on the Gallapagos Islands?
Scientists believe that there was originally one kind of finch that flew to the island from the mainland
The finches spread around the islands and started living in separate areas
Each area was unique with different climates and kinds of food to eat
These birds no longer breeded together so they stopped mixing their genetics (REPRODUCTIVE ISOLATION)
Over time the traits that were the most suited for the different parts of the islands were passed on and after many years the separate populations of finches looked very different and had changed so much from each other that they became different species

4. How are traits passed on? Pg 80L
Our physical traits are the result of our genes
Genes are made of DNA
Your DNA is separated into 46 chromosomes
You get 23 from each parent so you are an equal mix of genes from both
How these genes combine will determine what your physical trait will be
The genes you have are called your GENOTYPE
Your physical traits that come from your genes are called your PHENOTYPE
It is possible for your DNA to make a mistake and you will get a new gene different from both parents
This is called a MUTATION and can be beneficial for survival, can be harmful, or be neutral

5. How do genes combine to form a trait? 80L
For every trait you have, there is a gene from your mom and dad
For example: your dad might give you the gene for brown eyes and your mom might give you the gene for green eyes
In your genotype you have both genes so you can pass these on to your own children someday, but in your phenotype (your physical appearance) your eye color is determined by how these genes combine
If one of them is DOMINANT, it will overpower the other and will become your trait
If one is RECESSIVE, it is weak and will only appear in your phenotype if the other gene is also recessive

6. 80L/R
If both of your parents give you the same kind of gene (both genes are for brown eyes) then you are HOMOZYGOUS for that trait and will have brown eyes. When you have kids you can only give them a gene for brown eyes
If both parents give you different genes (brown and green) then you are HETEROZYGOUS for that trait and your eye color will be determined by which trait is dominant and recessive and when you have a child, you can give them the gene for either color
This is how traits can skip generations and show up rarely (like being the only person for generations with red hair)

7. How can we predict the traits of offspring?
If we know the genotypes of the parents and which genes are dominant and recessive, we can use Punnett Squares to predict the genotype and phenotype of their children
The genotype is written with letters that represent the trait (like B for brown eyes)
If the trait is dominant we use a capital letter: B
If the trait is recessive we use a lower case letter: b

8. We put the genotypes for each parent on the top and side of the Punnett Square and combine the genes.
For this example:
B = brown eyes (dominant)
b = green eyes (recessive)
All of their children will have brown eyes, but half of them are heterozygous and could pass the recessive trait for green eyes to their own children