2nd type of cell division Creates sex cells Meiosis 2nd type of cell division Creates sex cells The reason why ________ differ Genetic information of ________ is mixed No two sperm or ova are alike Ab AB ab aB

Asexual Reproduction Genetic ______ produced by _______ Works okay in ______ environments ____ population growth: all individuals bear young Binary fission Parent splits into 2 daughter cells Common among single-celled organisms Paramecium

2) Multiple fission _______ divides many times Cytoplasm divides many times Some cytoplasm for each _______ Amoeba:

A small clone “buds” from the adult’s ____ 3) Budding A small clone “buds” from the adult’s ____ Drops off and becomes independent Or stays connected and starts a ______ Hydra Sponge colony

4) Fragmentation If an adult gets broken into pieces, _________ can become a new individual flatworm Seastar

Evolution of sexual reproduction Might have began as a way to ______ damaged DNA Asexual species lack _________ chromosome pairs With chromosome prs from 2 individuals (parents), damaged one can be repaired _______ good one Began in early ____________ organisms, ~1.2 b.y.a. Had ______ to produce haploid sex cells (gametes)

Life cycle of sexually-reproducing species Starts with adults: Adults are made up of _______ cells = body cells Each cell has the full number of chromosomes 2n (paired set) = _______ number 46 in humans

Adults produce sex cells, or _______, by meiosis Occurs in _______ Halves the normal number of chromosomes Haploid sperm fertilizes _________ ovum Results in one _________ zygote Zygote develops into embryo, fetus, & baby Grows by mitosis Baby Adults Embryo mitosis fertilization Zygote (fertilized egg) Sperm meiosis Ovum

The human life cycle has diploid and haploid stages “n” = types of chromosomes “1n = haploid condition “2n” = diploid condition _________ Baby Adults mitosis _______ Zygote sperm meiosis fertilization ovum

How does meiosis differ from mitosis? Most stages are the same But meiosis separates chromosomes __________ 1st time during meiosis __ 2nd time during meiosis __

X X x x Prophase of Meiosis 1 Homologous chromosomes unite Referred to as _______ Tetrads X X x x Sketch 1

Homologous chromosomes swap parts Known as ______________ Point of Crossing over Nuclear envelope Results in _________ chromosomes Have a mix of parental information Sketch 2

X X x x Metaphase of Meiosis 1: ______ line up on metaphase plate Not individual chromosomes as in mitosis X x X x Metaphase plate Sketch 3

Crossed-over segments Anaphase of Meiosis 1 Homologous chromosomes get separated Not sister chromatids as in mitosis X x X x Crossed-over segments also get separated Sketch 4

X X x x Telophase of Meiosis 1 Results in __ daughter cells Sketch 5 Recall: Parent (diploid) cell had 4 chromosomes These have 2, one of each type X x Sketch 5

Next comes Meiosis 2: The second separation of chromosomes Similar to mitosis: _____________ get separated Not tetrads as in Meiosis 1 Somewhat different than mitosis in that: Starts with 2 _______ cells (result if meiosis 1) Ends with ___ haploid gametes

Sketch 6 Prophase of Meiosis 2 Metaphase of Meiosis 2 X X x x X x Same

different haploid ___ cells Sketch 7 Telophase of Meiosis 2 Anaphase of Meiosis 2    Results in 4 different haploid ___ cells      Recombined chromosome   Same  

Review: metaphase in mitosis versus meiosis 1 X x mitosis Meiosis 1 x X _______ _____________

X Meiosis provides genetic variation among ______ 1. Parts of parental chromosomes get exchanged = ______________ 2. Parental chromosomes position randomly across metaphase plate (orientation of tetrad) = _________________ X Vs.

x x x x x x x x x x x x x x x x x x x x 3. Orientation of homologous pairs along metaphase plate is independent = ___________________ Haploid cell no. 1 x x x x x x x x x x x x x x x (n=5 organism) x x x x x Haploid cell no. 2

Parthenogenesis (Greek: virgin creation) Some sexually-reproducing species can reproduce asexually (without genetic ______) Parthenogenesis (Greek: virgin creation) Embryos develop from unfertilized (haploid) _____ In early cell division, chromosome # gets _______ Some whiptail lizard populations are all _______ Also found in certain scorpions, aphids, bees, amphibians, & fish ____ are ecologically “expensive” because they can’t bear young Hermaphroditic/monoecious: individuals have genitalia of ____ sexes Common in flowering plants, invertebrate animals Dioecious: individuals have ______ sexes