• Reproduction is the creation of new individuals from existing ones

Sexual and asexual reproduction are both common among animals

• ASEXUAL AND SEXUAL REPRODUCTION

Reproduction

• In asexual reproduction

Asexual Reproduction

– One parent produces genetically identical offspring

• Binary fission

– Is the simplest type of asexual reproduction– Involves a single parent cell splitting through

mitosis into two genetically identical offspring cells

• Regeneration, is the re-growth of a whole animal from the pieces

• Budding

– Is the splitting off of new individuals from existing ones

• Asexual reproduction has a number of advantages– It allows a species to perpetuate itself if its

individual members are sessile or isolated from one another

– It allows organisms to multiply quickly

• One potential disadvantage of asexual reproduction is that it produces genetically uniform populations

Sexual Reproduction

Definition:

1. Process in which two cells, termed gametes, come together to form one fertilized cell that contains genetic information from both parental cells.

2. Production of offspring whose genetic constitution is a mixture of that of two potentially genetically different gametes.

• Advantages of sexual reproduction

– Increases genetic variation– Enhances reproductive success in changing

environments

• Disadvantage of sexual reproduction– Locating a mate

Meiosis

Quick Review -• Meiosis - division of cells which results in the

production of gametes

• Gametes - also known as sex cells, germ cells, or spores; cells of sexual reproduction, which contain only half the chromosomes of a normal cell

• Chromosomes - Threadlike bodies found in the nucleus, or center part, of a cell that carry the information of heredity.

• The usual purpose of meiosis is to form gametes- the sex cells that will fuse together to form a new diploid individual.

What is the point of meiosis?

To produce gametes

A sperm cell consists of:

•a head, which contains the nucleus

•a midpiece, which contains energy-releasing mitochondria

•a tail, which propels the cell forward

Head

Nucleus

Midpiece

Mitochondria

Tail

Male gametes • Male gametes, very large numbers

• 100 million sperm per ejaculation

• smallest cell in the human body

• Motile (if they can propel themselves, mobile if they can be easily moved)

Sperm Production (Spermatogenesis)

Video

Female gametes• Female gametes (ova or eggs in

animals, ovules in plants)

• Fairly small numbers.

• Human females for example release about 500 ova in a lifetime.

• Larger

• Stationary

• They often contain food reserves (lipids, proteins, carbohydrates) to nourish the embryo after fertilization

Spermatogenesis

Oogenesis

Occurs in the testesProduces 4 hapoid

cellsProduces 4 viable

spermatozoaMotile – swim with

tailProduction begins at

pubertyProduction continues

for entire life

Occurs in the ovariesProduces 4 hapoid

cellsProduces 1 Ovum & 3

polar bodies Nonmotile – moved

by currentsAll eggs present at

birthEggs mature from puberty to

menopause

Fertilization

http://www.doctoroz.com/videos/fertilization-animation

fertilization

http://images.suite101.com/292962_com_humanlifecycle3.jpg

Basic lifecycle of sexually reproducing organisms

http://www.youtube.com/watch?v=SOllUTBYZtE

Salmon spawning

Look for some disadvantages of this means of fertilization when watching this video

Types of fertilization: External

Types of fertilization: External

Human Reproduction

Battle of the sexes!!!

Are males & females all that different?

Well…….…..YES and NO

Same embryonic tissues becomes male or female reproductive organs.

Male or Female???• DNA determines baby’s gender

– XX = Female– XY = Male

All humans are female by defaultAt ~ 7 weeks the baby’s body may be “told” by DNA to become male

SRY gene located on the Y chromosome

Anatomy - similar

• Testicles & Ovaries – Glands responsible for the production of sex hormones and

gametes• Start inside body (Testicles “descend” before birth)

• Vas Deferens & Oviduct– Passageway of gametes

• Penis & Clitoris– Contain thousands of nerve ending to aid in sexual

stimulation

Fetus begins with “starter parts” that could develop into either gender.

Same tissue – Same function

Physiology – VERY different!

• Male– Uncomplicated– Produce sperm

•2-4 MILLION every day

• Female– Very Complicated!– Born with ~ 400,000

eggs• Uses ~500

– Ovulation• 1 egg “ripens” and is released

once a month

– Careful coordination of hormones & body

– Support life

The Male Reproductive System

Males

Produces male sex hormoneProduce 2-4 million sperm every day Outside body – why?Sperm like temps 1-2 cooler than body temp

Tube that carries sperm to the seminial vesicle and prostate

Temporary storage of spermDuring copulation, muscle contract to release sperm

Testes

Vas Deferens

Bladder

Epididymis

Prostate gland

Seminal vesicle

Urethra

Penis

Tube taking both urine and semen outside the bodyBulboureathral gland adds lubricant to aid travel of semen through the ureathra

Erected during copulation for insertion into vaginaDilation of arterioles causes the erectile tissue of penis become turgidSemen is squeezed from the penis to the top of vagina

Sperm

• Semen contains– 300-500 million sperm – 5%– Sperm food (fructose) – 30%– Alkaline fluid (pH buffer) –

65%

Why so many sperm?

Why a pH buffer?

What is sperm?

Head Contains chemicals to dissolve egg gooDad’s genetic information – one each of 44

autosomal chromosomes and 1 sex chromosome

MitochondriaEnergyContains mitochondrial DNA

from mother

Flagellum“tail” used for locomotion

• Human females have a reproductive cycle, a recurring series of events that produces gametes, makes them available for fertilization, and prepares the body for pregnancy

The Female Reproductive Cycle

The Female Reproductive System

Fallopian tube

Ovary

Uterus

Urinary bladder

Pubic bone

Urethra Vagina

Rectum

Cervix

Females

Vagina

Cervix

UterusOviduct

Ovary

For production of female gametes (ova/eggs)For production of female sex hormones

Carries the ovum forward by the beating action of the cilia on its inner surface and the contraction of muscles of oviduct

Allows for placenta to attachmentDuring embryo development it protects the embryo and provides a constant environment for the embryo to developDuring birth of baby it pushes the baby out by muscular contraction

Opening between the uterus and vagina

Birth canal

Menstrual Cycle

All about timing!!!Uterus must be ready when egg gets there in case it was fertilizedIf no fertilization, tear down lining of uterus and rebuild for next month

The Menstrual Cycle• The Menstrual Cycle

•The menstrual cycle is controlled by internal feedback mechanisms between the reproductive system and the endocrine system.

•The cycle takes an average of 28 days.

http://www.abpischools.org.uk/page/modules/hormones/horm4.cfm?cositenavigation_alltopic=1

Menstrual cycle

http://www.youtube.com/watch?v=9_tH8mLqXC8

Video (00:01:11)

The Menstrual Cycle

Ovulation

1.FSH causes the follicle to grow

2.Growing follicle releases estrogen

3.Estrogen ↑ the lining of the uterus

4.↑ levels of estrogen ↑production of LH

5.↑ LH causes the follicle to rupture releasing the egg (ovulation)

6. Ruptured follicle (corpus luteum ) produces progesterone

7. Since follicle is gone:

- ↓ in estrogen which causes

- ↓ in LH which causes

- corpus luteum to break down which causes

- ↓ in progesterone

8. Progesterone keeps the lining of the uterus from shedding, therefore ↓in progesterone = menstruation

**** if the egg does get fertilized, hormones will not drop and the uterine lining will be maintained for the entire pregnancy.

Estrogen Ovaries

Drop in levels causes shedding of uterine liningIncrease in levels causes uterine lining to thicken

Progesterone Corpus litheum (ruptured follicle)

Drop in levels causes shedding of uterine liningIncrease in levels causes uterine lining to thicken

LH (leuteinizing hormone) Pituitary gland & hypothalamus

Stimulates release of mature egg from ovary

FSH (follicle stimulating hormone) Pituitary gland

Acts on ovaries to mature the egg

HCG (Human Chorionic Gonadotropin) Corpus litheum (ruptured follicle)

Produced if fertilization occursStimulates continued secretion of progesterone

Hormones

Reproduction Hormones

Hormone Produced by Function

Testosterone Testicles Male sex traits

FSH Pituitary Stimulates egg/sperm development

Stimulate estrogen

LH Pituitary Stim. TestosteroneRelease of egg, corpus luteum, progesterone

Estrogen Ovaries Female sex traits

Progesterone Corpus luteum (Ovaries)

Maintains Uterus lining

• Q: How many of you have more than one parent?

– then, everyone in this room is a product of sexual reproduction

Characteristics of Sexual Reproduction

• Requires a female and male parent (i.e. it takes two to tango)

• Q: Why do we need more than 1 parent?

½ + ½ = 1

Characteristics of Sexual Reproduction

• Requires a female and male parent (i.e. it takes two to tango)

• Each parent donates ½ of the Chromosomes/Genes/DNA

• So, by what we’ve discussed, in sexual reproduction “mom” donates half, and “dad” donates half. How does this happen?

Characteristics of Sexual Reproduction

• Requires a female and male parent• Each parent donates ½ of the

Chromosomes/Genes/DNA• Requires fertilization - the combining

of gametes

• Now, nine months later, you come out kicking and screaming (and dancing).

• To which parent do you look exactly alike?

• How about your siblings? Do you look exactly alike one another?

Characteristics of Sexual Reproduction

• Requires a female and male parent • Each parent donates ½ of the

Chromosomes/Genes/DNA• Requires fertilization - the combining of

gametes• Produces genetic diversity - variation

among and within species that is attributable to differences in hereditary material.

So what can we conclude about Sexual Reproduction?

• it produces diversity

• diversity ensures survival of a species in an environment that changes