Reproduction and development

1. Asexual - one parent only

1. Unicellular organisms

1. fission- an equal division of genetic material and an equal division of cytoplasm. Example: paramecium.
2. Budding- an equal divison of genetic material, but an unequal division of cytoplasm. Example: yeast.

1. Simple multicellular animals

1. budding (hydra)

1. plants- vegetative propagation

1. runners- horizontal stems which travel along the ground.
2. Rhizomes- horizontal stems which travel underground.
3. Tubers- underground storage stems.

-photosynthesis

-produce excess glucose.

-sends out a rhizome and sends it to a tuber which stores starch and water.

-example: potato.

4. bulbs- underground stem with fleshy storage leaves.Ex.: tulips, onions.
5. Cuttings- take a part of a plant and it grows the missing sections to become a whole plant.

1. Regeneration- the regrowth of missing parts. It is possible due to a large number of indifferenciated (non-specialized) cells. Ex.: flaworms, planaria.

Mitosis- cell division of somatic cells. Characteristics: asexual reproduction; growth; repair; cancer- uncontrolled mitosis.

46è 92è 46, 46

Terminology

1. centrioles- the points of attachment for spindle fibers.
2. Spindle fibers- special protein threads to which chromosomes are attached.
3. Centromere- special part of the chromosome which attaches it to the spindle fiber.

1. centriole divides in 2.
2. 2 centrioles move in opposite directions until they’re 180° apart from each other. (see diagram).

1. chromatids- replicated chromosomes.

Mitosis

1. chromosomes replicate to form chromatid pairs.
2. Centriole divides and the 2 new centrioles migrate to opposite poles.
3. Nuclear membrane and nucleolus disappear.
4. Spindle fibers form.
5. Chromatid pairs attach to the spindle fibers (1 pair / spindle fiber).
6. Chromatid pairs migrate and line across the equator.
7. Centromeres replicate.
8. Chromatid pairs separate with individual chromosomes migrating to opposite poles (now has 2 nuclei).
9. Spindle fibers dissolve.
10. Nuclear membranes and nucleoli re-appear.
11. Cytokinesis- division of the cytoplasm.

1. animal cells- pinching in of the cell membrane.
2. Plant cells- formation of an equatorial plate (no pinching in because there is a cell wall).

1. Sexual reproduction- characteristics- one or two parents; gamete formation (meiosis- gamete formation, gametogenesis); fertilization (fusion of nuclei); offspring aren’t genetically identical to the parent.

What’s the difference between X meiosis and C meiosis?

X : Spermatogenesis- 1 primitive sex cell yields 4 mature sperm, all the same size, all are functional, all are haploid. Takes place in testes, at puberty, happens the whole life. Primitive sex cells are there at puberty as well.

C : Oogenesis- 1 primitive egg cell yields 4 cells: 1 ovum (egg) and 3 polar bodies- all are haploid, genetically all the same. Takes place in ovaries, only the ovum is functional, ovum is much larger than the polar bodies, happens at puberty, happens once a month, at the age of around 50- MENOPAUSE- cessation of female reproductive ability.

Polar bodies- get rid of extra chromorosome. "Genetic garbage cans-" make sure the ovum doesn’t thake in extra chromosomes.

46è 92è 46, 46è 23 (ovum); 23, 23, 23 (polar bodies).

Variations in sexual reproduction (in animals)

1. An organism with both X and C gonads (sex organs).

1. self-fertilization- 1 organism acting as both X and C parent (ex.- tapeworm- parasites).
2. Cross-fertilization- 2 organisms both of which act as both X and C parents (example: earthworm).
3. Differential development of gonads (ex.: oysters) (a sex change).

1. Parthenogenesis- embryonic development of an egg without fertilization (example: bees, wasps, hornets). Queen bee- mates once, gets all the sperm she needs. C (workers)= fertilized. X (drones)= unfertilized.

1. External fertilization and internal development- most fish, amphibians.

Characteristics: huge # of gametes and offspring; spawning season- a time of the year in which reproductive behavior is coordinated between the X and the C ; short period of embryonic development; while a zygote- "eat" small yolk; little or no parental care of offspring.

2. Internal fertilization and external development- birds, some mammals, some reptiles. Characteristics: intermediate # of offspring; parental care ranges from very intensive to non-existent; intermediate period of embryonic development; hardshell provides protection against dehydration, predators, disease, and adverse weather; shell is porous for gas exchange.

1. Amnion- acts as a shock absorber.
2. Chorion- functions in gas exchange.
3. Allantois- stores nitrogenous wastes (poisonous).

1. Internal fertilization and internal development- most mammals, some reptiles, some fish. Characteristics: large period of embryonic development, lots of parental care, small # of offspring.

1. X reproductive system

1. testes- produce sperm; produce testosterone; external- in a sac called a scrotum. Scrotal temperature is lower than body temperature- optimal for sperm production.
2. Vas deferens- sperm duct which transports sperm from the testes to the penis.

Vasectomy- X sterilization operation.

3. penis- transfers sperm to the vagina at the time of intercourse.

**Sperm is motile.** Urethra- common duct for both sperm and urine.

4. accesory glands- produce a collection of fluids which provides sperm with liguid environment for sperm motility, energy, and alkaline solution. These liquids are called semen. Semen + sperm

1. C reproductive system

1. ovaries- develop ova, produce estrogen and progesterone.
2. Oviducts (fallopian tubes)- transport ova from the ovaries to the uterus; site of fertilization (upper 1/3).
3. Uterus- site of embryonic development.
4. Cervix- neck of the uterus.