Y10 BIO - Patterns of Change

Natural selection

process by which organisms that are better suited to their environment tend to survive and produce more offspring.

Natural selection steps

1. Populations overproduce offspring.

2. There is heritable genetic variation in the population.

3. Selective pressure causes a struggle for existence.

4. There is differential survival and reproduction

5. Over generations, favorable heritable variations become more common, and are more likely to reproduce more offspring

Trait

observable characteristics of an organism that are heritable

Phenotype

observable expression of the genotype (words)

Genotype

symbolic representation of the alleles (symbol)

Test cross

x homozygous reccesive

Interphase

G1: growth and normal function

S: DNA replication

G2: preparation for cell division

Mitosis: Nucleas division

1. Prophase: DNA supercoil, Centrioles form spindle fibers, nucleas dissapears

2. Metaphase: Chromosomes line up along equator

3. Anaphase: Sister chromatids seperate to opposite poles

4. Telophase: Uncoil, nucleas repappears, Centrioles dissapear