Development Unit 4-4 Notes Mr. Hefti – Pulaski Biology

Step 1 – Meiosis in gonads Gametogenesis ◦Oogenesis egg / ovaries ◦Spermatogenesis sperm / testes

Step 2 – Fertilization Joining of egg and sperm Results in zygote (that makes more cells by mitosis) ◦Equation: 1N + 1N ￫ 2N Occurs where? ◦ Internal mammals, reptiles, birds ◦ External fish, amphibians

Cells split apart side-by-side Mitosis! Each cell has full DNA code to become any type of cell! All identical cells at this point (it’s now an embryo)! Step 3 – Cleavage

Step 4 – Differentiation Cells specialize based on what they are going to become Contain full DNA code - only use portion needed for that type of cell ◦Compare DNA code to recipe book

Step 5 – Development Unique DNA code of each organism controls structure and function Occurs where? ◦Internal for mammals (except marsupials and monotremes) ◦External for birds, reptiles, fish, and amphibians  Inside eggs, but outside mother’s body