EVOLUTION

Early Concepts of Evolution

Aristotle: nature evolved gradually from the simple to the more complex and from imperfect to perfect

Lucretius: wrote an evolutionary explanation of the origin of plants and animals

Leonardo da Vinci: put forward the theory of catastrophism
                              explains that fossil found in rocks resulted from a succession of fires and flood
                              that destroyed all things some time in the prehistoric past

Theory of Uniformatarianism

James Hutton: concluded that the formation of sedimentary deposits was due to geological forces
                       of erosion, sedimentation, uplift, and disruption on that were working in the past
                       and one continuing to the present

John Playfair: further explained and supported Hutton's concept

Sir Charles Lyell: proved beyond reasonable doubt the idea of geologic evolution through
                          his book Principles of Geology

GENETICS

Mendel's Princples of Inheritance

1. The F1 generation showed only dominant traits
2. In the F2 generation, both the dominant and recessive traits reappeared
3. In the F2 generation, there were 3x as many plants with the dominant traits than plants with recessive traits

LAW OF SEGREGATION
          - Mendel inferred that the two factors determining a trait segregates when the sex cells are formed
          - Each gamete (egg cell or pollen) is equally likely to contain either traits
phenotypes: trait of a plant (tall)
genotypes: the pair of alleles for that trait (TT or Tt)

LAW OF DOMINANCE

LAW OF INDEPENDENT ASSORTMENT
          - alleles of the gene pair for a particular pair of traits segregate independently of the alleles of gene pairs for the trait

MEIOSIS

MEIOSIS
          - type of cell division involving reproductive cells

Phases

Meiosis I
     stages:

Prophase I

• two sister chromatids of each chromosome pair up with the chromatids of its homologue (synapsis)
• makes up 90% of the entire process
• forms a structure called tetrads
• chromatids of homologous chromosomes exchange segments (crossing-over)
• nucleoli and nuclear membrane start to disappear

Metaphase I

• homologous chromosomes align at the middle of the cell

Anaphase I

• movement of the chromosomes of each homologous pair toward the opposite poles of the cell
• individual chromosome still consist of two sister chromatids

Telophase I and Cytokinesis

• chromosomes are on each side of the pole
• chromosome still consist of two sister chromatids
• nucleoli and nuclear membrane reappear

Meiosis II
     stages:

Prophase II

• starts with haploid cells
• nuclear envelope starts to breakdown

Metaphase II

• chromosomes line up along the cell equator

Anaphase II

• chromosomes are pulled toward the opposite poles of the cell

Telophase II

• chromosomes finish their migration to poles
• nuclear membrane forms again and nucleolus reappear

Cytokinesis

• four new daughter cells are produced, each with a haploid number of chromosomes

MITOSIS

VOCABULARY :

• Cell Division - process by which cell reproduce
• Chromosomes - cell parts that determine what traits a living thing will have
• Chromatid - one strand of DNA, after replication, a chromosome is made up of two identical chromatids
• Daughter Cells - new cells produced by cell division
• Cytokinesis - a division of the cytoplasm of one parent cell into two daughter cells

Interphase
          - DNA has replicated but has not formed the condensed structure of chromosome. They remain as loosely coiled chromatin. The nuclear membrane is still intact to protect the DNA molecules from undergoing mutation.
   G1
   S - synthesis (DNA)
   G2

Early Prophase
          - the nuclear membrane breaks down
          - chromosomes shorten and thicken
          -centrioles are forming

Late Prophase
          - centriole pairs move apart
          - nuclear envelope starts to break up

Metaphase (midddle)
          - the chromosomes are lined up along the cell's equator
          - are attached to the mitotic spindle

Anaphase (away)
          - the newly formed chromosomes are pulled toward opposite poles of the cell

Telophase
         - the chromosomes have finished their migration to the poles
         - the plasma  membrane of the cell pinches down along the equator
         - the nuclear membrane forms again and the nucleolus reappears

Cytokinesis
         - after mitosis, two diploid daughter cells have formed