Interphase What the cell spends 90% of its time doing. Divided into G1,S, and G2 stages This is where the cell goes about basic life functions of growth, DNA copying and regulation

During this stage new organelles are being synthesised, so the cell requires both structural proteins and enzymes, resulting in great amount of protein synthesis. In short the cell grows (Growth phase)

synthesis phase, is a period when DNA synthesis or replication occurs.DNA synthesisreplication

Cell grows more and prepares to divide

Cell cycle

(The M phase) Before We Split mitosis= the division of a cell's nucleus. Along with cytokinesis (the division of the rest of a cell), mitosis results in a parent cell dividing into two daughter cells. The genetic information within each of these daughter cells is identical.

This is how we get sister chromatids

Sister chromatids pair up Spindle fibers form Nuclear envelope breaks down Spindle fibers (microtubules) attach

Chromosomes line up in the center of the cell ½ of each chromosome (1 chromatid) is pulled to each pole of the cell

Nuclear envelope reforms

Cytokinesis (the final step) Cytokinesis is the process of splitting the daughter cells apart. Whereas mitosis is the division of the nucleus, cytokinesis is the splitting of the cytoplasm and allocation of the golgi, plastids and cytoplasm into each new cell.

Prophase I Homologous chromosomes pair up (each made up of 2 sister chromatids) Homologous chromosomes swap some allele information Nuclear envelope disappears

Metaphase I Chromosomes line up down the middle Spindle fibers attach See information is swapped

Anaphase I 1 of each of the Homologous chromosomes is pulled to each side of the cell

Telophase I & Cytokinesis The cell divides down the middle Nuclear envelope sometimes reforms

Telophase I & Cytokinesis The cell divides down the middle Nuclear envelope sometimes reforms

No new Interphase!

Prophase II Spindle fibers form Nuclear envelope disintegrates

Metaphase II Chromosomes line up in the center of the cell Spindle fibers attach

Anaphase II Sister chromatids separate

Telophase II & Cytokinesis Nucleus reforms Note that each of the four cells is haploid

Taken from ex.html

Comparing the Two

Homologous chromosomes swap information in meiosis In meiosis 1 homologous chromosomes not sister chromatids are separated Meiosis ends with 4 daughter cells, Mitosis ends in 2

Types of Cells Somatic  Any cell that is not a sex cell: egg (ovum) or sperm  Contain 46 chromosomes in humans

Types of Cells Sex Cells (gametes)  sex cells (egg or sperm)  Contain 23 chromosomes in humans 22 autosomal chromosomes & 1 sex chromosome

Y X

Sex Chromosome X & Y Females XX & Males XY

Autosome- all chromosomes that are not X or Y

Diploid All somatic cells are diploid meaning they have a full set of 46 chromosomes This is represented by the denotation 2n

Haploid All sex cells are haploid meaning they have a half set of 23 chromosomes This is represented by the denotation 1n

Fertilization Fertilization- is the fusion of the two gametes after sexual intercourse (sperm from the father and ovum from the mother) The resulting fertilized diploid egg is known as a zygote 23 chromosomes from the father and 23 from the mother

How Do We get From

Animal Reproduction

ASEXUAL REPRODUCTION “the creation of new individual's whose genes all come from one parents without the fusion of egg and sperm.” -Campbell Biology Essentially Cloning the Parent

ASEXUAL REPRODUCTION Organisms are well adapted to stable environments cloning maintains the “best combination for the current situation” Less of a chance to introduce detrimental traits into the gene pool No need to find or compete for mates (saves time and energy and can reproduce in isolation) Can produce a large amount of offspring in a short amount of time

Asexual reproduction is best suited to stable environments in which individuals are already well adapted to survive This is because the “best traits” are identically copied into each successive generation ASEXUAL REPRODUCTION

Fission The splitting of a parent into two roughly equal sized offspring

Common among invertebrates Protozoan mag/art98/celldiv.html

Budding A new individual growing from and then splitting off from the parent The new offspring will either detach or remain attached to the parent. (This is common in tunicate, and cnidarians such as coral or hydra

udding_LP.jpg Hydra

Hydra

Gemmules Aggregates of several types of cells that are surrounded by a protective coating in sponges

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Fragmentation & Regeneration This occurs when an adult is broken into pieces and these pieces grow into new adult organisms. This is common among sponges, cnidarians, and tunicates.

SEXUAL REPRODUCTION “the creation of Offspring by the fusion of haploid gametes to form a zygote, which is diploid.” -Campbell Biology

SEXUAL REPRODUCTION Adds more variety to the population so as a whole the population is better situated to survive and prosper in rapidly changing or new environment Best in new or rapidly changing environment

Effects of sexual reproduction The Red Queen in “Alice in Wonder Land” had to run at full speed just to stay in the same place. This means that “a species must continually evolve to survive in a world full of other evolving species” –the science of ecology

One example are diseases. A cloned (or asexually reproduced) population is highly susceptible to being wiped out by a contagion. Predator prey relationships are another example

Sexes aren’t necessarily fixed or essential. Some species of frogs and tropical fish for example, change sexes depending on population dynamics (sometimes several times).