Asexual Reproduction

invertebrates usually have asexual tendencies

budding

regeneration

parthenogenesis

new individual forms as an extension of an adult

ie. Hydra!

part of an organism was severed; parents grow a replacement

ie. sea stars!

"virgin production"

development of unfertilized eggs

exhibit sexual behavior with no males!

ie. whip tail lizards

Sexual Reproduction

3 Steps

mating is time consuming and risky

production of diversity > cost of sex

gametogenesis
spawning / mating
fertilization

occurs in gonads

males = flagellated sperm

females = sessile eggs or ova

germ cells produce spermatogonia or oogonia

mitosis results in primary spermacyte or oocyte

begins with primary spermacyte

meiosis I and II produce secondary spermatocytes and spermatids 

(connected via cytoplasmic bridges)

spermatids mature and differentiate into 4 sperm

many females never mate

females diploid, males haploid

queen sexes 15-20 males on her first day

collects enough sperm to last an entire lifetime

males explode after sex. HAHAHAHA

Oogenesis:

Primary Oocyte

enters prophase of meiosis I

stay there until puberty (8 yrs) or menopause (60 yrs)

acquires energy, raw material, and RNA needed to support the embryo

Oogenesis:

First Meiotic Division

results in 2 daughter cells

one (secondary oocyte) is larger than the smaller polar body

Oogenesis:

Second Meiotic Division

results in large ootid and two polar bodies

these degrade (sometimes incompletely until fertilization)

end product = ovum!

union of sperm and egg

results in formation of the zygote

sperm/egg recognition

sperm activiation

plasma membrane fusion

subesequent blockage

metabolic activity in the egg

fusion of nuclei

some eggs produce peptides specific for same species sperm

prevents random cells from attacking the egg

human eggs don't signal to the sperm.

Obstacles:

Jelly Coat (humans: cumulus)

Vitelline envelope (zona pellucida)

protect the egg;

acrosome releases digestive enzymes to eat jelly coat

bindin extends from sperm and is recognized by receptors on vitelline envelope

plasma membrane fuse and sperm nucleus can access egg nucleus

initiated by fusion of plasma membranes:

one sperm --> egg

change in electric charge from - to +

happens in seconds, lasts about 1 minute

vitelline membrane ---> physical barrier

impenetrable to sperm

facilitated by cortical granules

external fertilization

internal fertilization

aquatic species

females release a shitload of eggs

males release a shitload of sperm

synchronization, mutual stimulation, behavior ensure fertilization

terrestrial

sperm are released into female reproductive tract

seen with spermatophores

males deposit sperm packets and females find it

OR 

males deliver it to females

occurs in mites, scorpions, squid, spiders, some salamanders

external sex organs

pieces must fit

some penises have scoops to remove sperm of previous males (EWW) and replace it with their own

monoecious - both sexes on one organism

doubles chances of finding a mate

male and female at the same time

sperm exchange = fertilization of eggs in each individual

ie Lumbricus

can be male or female at different times in life

all born male ; largest becomes girl

siblings can be all male or all female to prevent inbreeding

ie clownfish!

insects, reptiles, birds

eggs are laid in the environment

protection is common

nutrients are in egg

egg is retained inside the mom's body

all vertebrate groups except :

crocodiles, turtles, birds

found in mammals

nutrient and waste exchange

eggs retained in mother until they hatch

ie. garter snakes and guppies!

accessory organs are crucial

not directly involved in reproduction

important for mating and sexual dimorphism

5% sperm

fluid

molecules to support sperm and fertilization

liquid to sperm

60% of semen volume

holds alkaline liquid

30% of semen volume

provides lubrication for ejaculation

old sperm

pre ejaculate - can get you pregnant!

sensitive skin

stimulation promotes ejaculation

increased blood flow to spongy tissue

result of stimulation

rhythmic contraction of smooth muscles

moves semen to base of penis

contraction of muscles at the base of the penis

forces the semen out of the urethra

facial hair

deep voice

pubic hair

increased muscle mass

produces eggs

receives sperm

nurtures the embryo

tube to the uterus

where fertilization occurs

muscular organ with cavity for development

pee after sex to get dirty penis bacteria out

lining of the uterus

implantation

placenta

lining gets hard & overstays its welcome

painful cramping 

can lead to sterilization :O

neck of the uterus

remains closed until birth

(dilation)

semen receptacle

birth canal

anterior tip of labia minora

stimulation

produces a mature egg

follicle - functional unit of ovary

28 days

ovulation of one egg (2ndary oocyte) occurs on 14th day

prepares uterine for a fertilized egg

build up of highly vascularized endometrial tissue

becomes placenta or is shredded

hypothalamus - gonadotropin releasing hormone (GnRH)

anterior pituitary - follicle stimulating hormone (FSH)

anterior pituitary - luteinizing hormone (LH)

Lydig cells - testosterone

Sertoli cells - inhibin

GnRH

FSH

LH

ovary - estrogen and progesterone

implantation of blastocyst - human chorionic gonadotropin (hCG)

bonding hormone - childbirth

mama and baby love

Human Sexual Response

(Four Phases)

excitement

plateau

orgasm

---refractory period in males - prolactin---

resolution

abstinence - 0% error

sterilization - < 0.15%

female hormone therapies - < 6%

barrier methods - 10-25%

rhythm method - 15-35%

coitus interruptus - 20-40%

no prevention attempts - 85%

miscarriage

half of unwanted pregnancies are terminated

1.5 million per yr

danger for the mother

prenatal testing reveals birth defect

fertility control 

15% of couples try but can't get pregnant

artificial insemination

assisted reproductive technologies

intracytoplasmic injection

egg and sperm are joined in lab

inserted into female for development

ie. in vitro fertilization, test tube babies

determines whether a genetic defect is present as early as the 8 cell stage!

WOAH