Asexual & Sexual Reproduction Reproduction & Development

Key Ideas 2.1d – In a sexually reproducing organisms, all the genes come from a single parent. Asexually producing offspring are normally genetically identical to the parent. 2.1e – In sexually reproducing organisms, the new individual receives half of the genetic information from its mother (via the egg) and half from its father (via the sperm). Sexually producing offspring often resemble, but are not identical to, either of their parent. 4.1d – The zygote may divide by mitosis and differentiate to form the specialized cells, tissues, and organs of multicellular organisms. 2.1j – Offspring resemble their parents because they inherit similar genes that code for the production of proteins that form similar structures and perform similar functions.

Reproduction Reproduction – life process by which living things produce other living things of the same species Not necessary for life; however, it is necessary for the continued survival of a particular group of organisms Species must reproduce regularly in order for a species to survive from generation to generation Types of Reproduction – Asexual reproduction – requires only one parent and results in large numbers of genetically identical offspring Sexual reproduction – involves two parents and the offspring is genetically different from the parent cells

Cell Reproduction Cell Division – a complex series of changes in the nucleus of a cell that leads to the production of new cells Types of Cell Division – Mitosis – results in two daughter cells identical to the parent cell and to each other Meiosis – results in daughter cells that contain half the number of chromosomes found in the parent cells and occurs only in gamete formation

Cell Reproduction Vocabulary Diploid (2n)– when a cell contains two sets of chromosomes, usually one set from the mother and another set from the father. Body Cells resulting from mitosis are diploid Haploid (n)- when a cell only contains one set of chromosomes Gametes (sex cells) resulting from meiosis are haploid

Mitosis All body cells (except sex cells) are produced by mitosis Produces 2 daughter cells 1 Cell division Daughter cells have the same number and type of chromosomes as the parent cell If a parent cell is diploid (2n), then the resulting daughter cells are diploid (2n) Mitosis = Asexual Reproduction Daughter Cell is genetically identical to parent cell In multicellular organism, results in growth and repair of body tissues In one-cell organisms, form of asexual reproduction

Phases of the Cell Cycle Interphase Mitosis 2A. Prophase 2B. Metaphase 2C. Anaphase 2D. Telophase Cytokinesis

Phases of the Cell Cycle Have a student come up and point out each phase Find and Insert video clip

Meiosis Sex cells (gametes = sperm & egg cells) are produced by meiosis Produces 4 daughter cells 2 cell divisions Daughter cells contain one-half of the chromosome number as the parent If a parent cell is diploid (2n), then the resulting daughter cells are haploid (n) Daughter cells are genetically different than parent cells Meiosis = Sexual reproduction When sperm and egg cells unite during fertilization, species’ normal chromosome number is restored

Meiosis Consist of two separate divisions Meiosis I Meiosis II Starts with 1 Diploid (2n) cell and results in 2 Diploid (2n) cells Meiosis II Starts with 2 Diploid (2n) cells and results in 4 Haploid (n) cells Males = 4 Haploid sperm cells Females = 1 Hapoid egg cell and 3 haploid polar bodies

A. Prophase I (Crossing over occurs) B. Metaphase I C. Anaphase I Phases of Meiosis I 1. Interphase 2. Meiosis I A. Prophase I (Crossing over occurs) B. Metaphase I C. Anaphase I D. Telophase I

Types of Asexual Reproduction Binary Fission – parent cell divides into two daughter cells of approximately the same size Budding – division of the cytoplasm is unequal and the offspring is smaller than the parent cell Sporulation – formation of spores (specialized reproductive cells that contain a nucleus and a small amount of cytoplasm Regeneration – development of a new organism from a part of the parent organism Vegetative Propagation – part of a plant grows into a new plant

Sexual Reproduction Sexual Reproduction : Recombination of chromosomes = Increased genetic variation Increased genetic variation = Increase an organism’s chances for survival and play a significant role in species evolution Includes the fusion (joining) of two sex cells formed during meiosis Sex cell nuclei fuse during fertilization forming a fertilized egg called a zygote. Zygote will then divide by mitosis and develop into a new organism Gametes – mature sex cells (egg and sperm cells) Gametogenesis – sex cell formation involving meiosis of immature sex cells. Two types Spermogenesis – formation of sperm cells Oogenesis – formation of egg cells

Spermogenesis Oogenesis Occurs in Males Occurs in testes Produces 4 sperm cells Motile (can move) ½ genetic material Haploid cell (n) Occurs in Females Occurs in ovaries Produces 1 egg cell and 3 polar bodies (small, non-functioning cell that disappears) Non-motile (not able to move) ½ genetic material Haploid cell (n)

Fertilization Fertilization – union of egg and sperm cell nuclei that restores the chromosome species number Types of Fertilization: Internal Fertilization – takes place inside the body of the female where the male deposits its sperm inside the reproductive tract of the female External Fertilization – takes place in a water environment outside the body of the female

Internal Development Embryonic development begins immediately after fertilization Zygote undergoes repeated cell divisions by mitosis called cleavage Developing organism is called the embryo Beginning Steps: Solid ball of cells form (morula) Center of ball becomes hollow (blastula) One side of the ball folds inward forming a second, inner, layer of cells (gastrula) Three germ layers form – ectoderm, mesoderm, endoderm Division continues and form all the tissues, organs and organ systems by the process of differentiation