Reproduction An quick over view

Asexual Reproduction Many organisms reproduce asexually –Bacteria DNA replicates and cell divides = Binary Fission –Budding as in Yeast and sponges –Vegetative propagation- take a cutting or spreads from root. –Parthenogenesis- in some lizards, fish and insects females can produce offspring from an unfertilized egg. –Spores- Fungus, Ferns and some mosses produce asexual spores.

Binary Fission DNA Replicates Chromosomes split Cytokinesis Two smaller cells Genetically Identical

Asexual reproduction There is no genetic change from generation to generation. Offspring are basically clones of parent (genetically identical) No need to mate Single individual may reproduce…even if they are stuck on a island alone… Population may be more susceptible to disease, environmental change or other problems

Sexual Reproduction 2 haploid (1n) gametes (Such as Sperm and Egg) unite to form a diploid (2n) Zygote

Diploid vs Haploid These terms refer to the number of sets of chromosomes and organism has. Humans are Diploid, we have two sets of chromosomes 46 total or 23 Pairs of “Homologous” chromosomes Sperm and eggs are haploid they only have 23 chromosomes each. When sperm and egg join the resulting zygote will have 46 chromosomes

Homologous Chromosomes Homologous means “Like” or “Same” Homologous chromosomes are chromosomes that code for the same genes. Remember that a gene codes for a protein that may result in a trait. The homologous chromosomes may have different version of the genes called “Alleles” They code for the same trait but may have different forms or colors.

Meiosis The process of making a haploid cell Also known as a reduction division because the number of chromosomes is reduced in this process. Two stages –Meiosis I –Meiosis II –Results in 4 haploid (1N) Gamates

–Meiosis I –DNA is Replicated Homologous chromosomes line up in metaphase. This is when genetic recombination can occur… so not all offspring from the same pair will be identical! Very important for variation within a population and for the rise of new species. -Results in 2 hapliod cells –Meiosis II –DNA in NOT replicated in the two haploid cells, chromatids separate and divide, results in 4 hapliod (1n) cells.

Meiosis I

Meiosis II Prophase IIMetaphase IIAnaphase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II Telophase II Meiosis II results in four haploid (N) daughter cells. Prophase IIMetaphase IIAnaphase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell.