CHARACTERISTICS OF LIVING THINGS Remember: CHARACTERISTICS OF LIVING THINGS All Living things reproduce

Asexual Reproduction Bacteria reproduce using Binary Fission

PRODUCES CELLS THAT ARE IDENTICAL COPIES OF PARENT CELL Binary Fission & Mitosis

Asexual Reproduction Advantages Disadvantages Can make offspring faster Don’t need a partner Disadvantages Species CAN’T change and adapt One disease can wipe out whole population

Sexual Reproduction Combines genetic material from 2 parents (sperm & egg) so offspring are genetically DIFFERENT from parents

+ EGG SPERM  If egg and sperm had same number of Zygote (One celled organism that has 46 chromosomes) If egg and sperm had same number of chromosomes as other body cells . . . baby would have too many chromosomes!

Sexual Reproduction ADVANTAGES DISADVANTAGES Allows for variation in population Individuals are different Provides foundation for EVOLUTION Allows species to adapt to changes in their environment Takes longer to reproduce Need a mate Mutations can occur easily

MEIOSIS is the way… to make cells with ½ the number of chromosomes for sexual reproduction

HOMOLOGOUS CHROMOSOMES MOST CELLS HAVE 2 COPIES OF EACH CHROMOSOME = DIPLOID 2N (ONE FROM MOM; ONE FROM DAD) ALL BODY (SOMATIC) CELLS ARE DIPLOID HOMOLOGOUS CHROMOSOMES DIPLOID & HAPLOID

Diploid & Haploid Cells Some cells have only one copy of each chromosome = HAPLOID 1n All sperm and egg cells are haploid

REMEMBER MITOSIS Makes 2 cells genetically IDENTICAL to parent cell & to each other Makes 2n cells Makes SOMATIC (body) cells Used by organisms to: increase size of organism, repair injuries, replace worn out cells

MEIOSIS Makes 4 cells genetically different from parent cell & from each other Makes 1n cells Makes GERM CELLS or GAMETES (sperm & egg) Used for SEXUAL REPRODUCTION

Lets Take a Closer look at Meiosis MITOSIS: G1 S G2 P M A T C        MEIOSIS: G1 A T C ( I ) S G2 P M        P M A T C ( II ) 

MEIOSIS l

Meiosis ll Prophase II Metaphase II Anaphase II Telophase 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 results in four haploid (N) daughter cells.

http://www.youtube.com/watch?v=D1_- mQS_FZ0

WHAT MAKES MEIOSIS DIFFERENT ? SYNAPSIS & CROSSING OVER (PROPHASE I) SEGREGATION & INDEPENDENT ASSORTMENT (ANAPHASE I) 3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT… ONLY COPIES DNA ONCE

WHAT MAKES MEIOSIS DIFFERENT ? Homologous chromosomes pair up during PROPHASE l = SYNAPSIS This group of FOUR (4) chromatids is called a TETRAD (4)

WHAT MAKES MEIOSIS DIFFERENT? 1. Exchange of DNA between homologous pairs = _____________ during PROPHASE l CROSSING OVER Allows shuffling of genetic material (more variation Between organisms) http://www.youtube.com/watch?v=op7Z1Px8oO4 http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

HOMOLOGOUS CHROMOSOMES SAME SIZE SAME SHAPE CARRY GENES for the SAME TRAITS BUT NOT IDENTICAL! (Don’t have to have the SAME CHOICES)

CROSSING OVER rearranging of DNA Allows for_________________ in different combinations After crossing over, chromatid arms are________________ anymore NOT IDENTICAL

WHAT MAKES MEIOSIS DIFFERENT ? 2.Separation during ANAPHASE I SEGREGATION & INDEPENDENT ASSORTMENT Separates gene choices and allows shuffling of genetic material

SEGREGATION (Anaphase I) http://www.biostudio.com/d_%20Meiotic%20Recombination%20Between%20Unlinked%20Genes.htm