Reproduction

Asexual Sexual Mitosis and Meiosis

Reproduction

 A species is a group of closely related organisms that share certain characteristics and produce new individuals.

 For many species to survive past a single generation, reproduction is essential. All individuals eventually die, but a species continues because of reproduction.

 When individuals reproduce, their offspring begin a period of development that ends in adulthood. Once an individual reaches adulthood, it is usually able to reproduce and continue the species for another generation.

 Reproduction and development are necessary for the continuation of any species and the continuation of life.

Types of Reproduction:

 Asexual  Sexual

1. Asexual Reproduction

:

 Involves 1 parent  All single celled organisms  Examples: Amoeba, Paramecium, Bacteria  Some multicellular organisms  Examples: Some plants (spider plant, strawberries), hydras, earthworms, starfish  Genetically identical offspring  By the process of mitosis

Review Mitosis

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Mitosis

: “My toe grows by Mitosis”  the division of the cell nucleus into 2

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Mitosis Animation

SUMMARY OF MITOTIC CELL DIVISION Points of Comparison Mitosis

Number of cell divisions Exchange of genetic material between chromosomes Number of functioning cells produced from the original 1 No 2 Genetic makeup of final cells produced Function of cells produced in multicellular organisms Same as original Growth or replacement of body cells

Diagram of Mitosis

2. Sexual Reproduction:  Involves 2 parents  Most multicellular organisms  Genetically different offspring  By the process of meiosis  Growth by mitosis

Asexual Reproduction:   1.

2.

3.

4.

5.

All types of asexual reproduction produces offspring that are identical to their parents.

There are 5 types of asexual reproduction: Binary fission Budding Sporulation Regeneration Vegetative Propagation

Binary fission         Simplest form of asexual reproduction common in unicellular organisms examples: paramecium, amoeba, bacteria Mitosis Equal distribution of nuclear materials and cytoplasm End result: 2 new organisms (daughter cells) identical contents parent no longer exists only difference is smaller in size

Mitosis

Budding       Parent divides into two daughter cells with unequal distribution of cytoplasm The smaller cell is called the BUD.

Budding refers to the production of a multicellular outgrowth from the parent organism parent organism = the original cells the bud and the parent may detach from each other and live independently or may remain together to form a colony Parent and offspring are not the same size in the end

 Examples of organisms the reproduce by budding:  Hydra  yeast

Yeast

Hydra

Sporulation     Spores are produced by mitosis Spores are specialized reproductive cells and are unicellular They have a thick protective coat that keeps them safe when environmental conditions are unfavorable They stay dormant until conditions become favorable for temperature and moisture and develop into a new individual

 Examples: Bread mold, mushrooms

Regeneration    The development of an entirely new individual from part of the original by the process of mitosis Also refers to the replacement of lost structures Not usually the form of reproduction for organisms

 The power of regeneration decreases as the organism becomes more complex.

 The cells of multicellular organisms tend to be more differentiated. Differentiation is the process that transforms developing cells into specialized cells with different structures and functions. Ex: liver cell vs. brain cells

 Lobsters and crabs regenerate claws (note: They can not regenerate an animal from the claw !

 If a hydra is cut in half, each half will grow a new individual

 A planarian can be cut into several pieces, each piece will grow into a complete worm

 Star fish can develop from a single ray and a piece of the central disk

  Mammals can regenerate some tissue Example: Liver

Vegetative Propagation      Some multicellular organisms reproduce by this method New organisms develop from root, stems, or leaves of the parent plant Can occur in 2 ways: Artificially (human influence) naturally (runner, tubers, or bulbs)

1.

Artificial Vegetative Propagation

:  Developed by farmers and gardeners that allow them to grow plants with desirable traits  Examples: spider plants, seedless orange tree

Advantages of Artificial Propagation:

 New plants have the same make up as the parent  It takes less time to mature  Seedless fruit can be grown  Faster growth of fruit or nuts  Higher levels of fruit or nut production

Compare/Contrast Table Method Cuttings Grafting Budding Comparing Plant Propagation Methods Procedure

A length of stem that includes lateral buds is cut from the parent plant and partially buried in soil or rooting mixture to take root.

A piece of stem is cut from the parent plant and attached to another plant.

A piece of lateral bud is cut from the parent plant and attached to another plant.

2.

Natural Vegetative Propagation

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 Occur naturally without human intervention  Examples: runners, tubers, bulbs

Runners Tubers Bulbs Examples

Strawberry Grasses Potatoes Tulips Onions Lilies

Picture or Diagram

What is Cloning?

 A technique that accomplishes the same end results as asexual reproduction (Identical copies)  Clones are very common in asexual reproduction

How animals are cloned:

1.

2.

3.

4.

5.

Nucleus of parent cell is removed Nucleus is inserted into an egg cell in which the nucleus has been removed Egg cell is implanted into body of female, where it develops Result: Organism with not 50% of the genetic information from 1 parent, but 100% The clone is 100% identical to the original parent (step 1)

 Cloning has been accomplished in animals as complex as sheep and pigs

Scientists are also developing methods in which we can grow human body parts.

Human Reproduction and Development  Human reproduction and development are carried out by specialized organs.

 The functions of these organs are regulated by factors such as gene expression, hormones, and the environment .

 The reproductive cycle in both males and females is regulated by hormones such as testosterone, estrogen, and progesterone. The hormones are controlled by the endocrine system in humans.

 In humans, as a in nearly all mammals, fertilization and development occur internally within the mother’s body. Reproductive organs in other mammals are similar in appearance and function.

 Reproduction is absolutely essential to the continuation of the species. Without it, a species will cease to exist.

Note:

Sex cells = gametes = egg or sperm

Male Reproductive System  The structures and functions of the male reproductive system, as in other mammals, are designed to do the following: 1. Production of gametes (Sperm) 2. Delivery of gametes

Testes:   male reproductive organ produce sperm  develop with in abdominal cavity and descend to the scrotum   also referred to as gonads produce sperm and testosterone  number = 2

 The testes have clusters of tiny tubules called seminiferous (means seed bearing) tubules. They are tightly coiled and twisted together to form a compact organ.

 The pituitary gland releases Follicle Stimulating Hormone (FSH) and Leutenizing Hormone (LH), which stimulates the testes to produce the male sex hormone testosterone.

 Testosterone is responsible for the development of secondary sex characteristics that appears in males at puberty.

 Male Secondary Sex Characteristics: A boy’s voice becomes deeper, he grows a beard and more body hair, his chest broadens, he may find it easier to develop large muscles.  He will continue to grow for several years after his female classmates have stopped growing.

 FSH and testosterone stimulate the development of sperm. When large numbers of sperm have been produced in the testes, the development process of puberty is completed.  The reproductive system is now functional, meaning that the male can produce and release active sperm.

Sperm:  Sperm cells are haploid (1n) gametes produced via gametogenesis in the testes to form the haploid nuclei found in male sperm.

The sperm consists of the following:

 Head: contains the highly condensed nucleous (DNA = genetic information from the male)  Midpiece: packed with mitochondria which produce energy for the sperm to move  Tail or flagella: propels the cell forward

Scrotum:  The scrotum is a sac like structure that holds the testes on the outside of the body.

 It regulates the temperature of the testes by relaxing when the body is hot and contracting when the body is cold.

 The testes remain in the scrotum, outside the body cavity, where the temperature is about 1-3 ° lower than the internal temperature of the body (37 °C) Sperm development requires the lower body temperature.

Epididymis:  located on the top of the testes  Coma shaped structure in which sperms are fully matured and stored.

 After a brief storage in the epididymis, the sperm are forced into a tube known as the vas deferens.

Vas deferens

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 A tube that connects the epididymis to the prostate gland  It is cut during a vasectomy to sterilize the male.

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Animation of Vasectomy

Prostate Gland

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 Secretes a fluid that allows sperm to swim

Prostate Cancer

Seminal Vesicles

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 Secretes a sugary substance that provides nutrients to the sperm  Why does the sperm need sugar?

Cowper’s Gland

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 Secretes a basic solution to neutralizes the acidity of the vagina  Also known as the

bolbourethra

Urethra

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 Merges with the vas deferens  The tube inside the penis that carries semen and urine out of the body

Penis

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 Contains the urethra  Used during intercourse to ejaculate sperm into the vagina

Semen

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 Sperm plus the fluid that is ejaculated out of the penis  Between 100 and 200 million sperm are present in 1 milliliter of sperm, Which is 5 million sperm per drop. If they are released in the female reproductive tract of a female, the chances of a single sperm fertilizing an ovum, if one is available are quite good.

The Male Reproductive System

Section 39-3 The Male Reproductive System

Large intestine Rectum Seminal vesicle Prostate gland Cowper’s Gland Epididymis Testis Urinary bladder Vas deferens Urethra Penis Scrotum

Female Reproductive System  1.

The female reproductive system is organized to do the following: produce gametes 2.

3.

exchange materials through the placenta provide milk to the offspring

Ovaries

:

 The primary reproductive organs in the female and are located in the abdominal cavity.

 The female gonads  Females have 2 gonads about the size of an almond  Eggs are produced, mature, and are stored in the ovaries.

 Usually only 1 egg is produced per month

 The ovaries produce the hormones estrogen and progesterone, which are associated with sexual development  Each time an ovum is released, the body of the female must be prepared to develop the developing embryo  As in males, puberty in females start with changes in the hypothalamus (brain) that causes the release of FSH and LH from the pituitary gland

 Note: FSH and LH are the same hormones that are found in males, although their target cells and effects they produce in females are quite different  FSH stimulates cells within the ovaries to produce the hormones known as estrogens. The estrogens cause the reproductive system to complete its development and to produce the secondary sex characteristics that appear in females.

Female Sex Characteristics:

 Enlargement of the breasts and reproductive organs, widening of the hips, and growth of hair in the armpits and pubic area

Primary Follicle:  The primary follicle is an immature egg found in the ovary  Females are born with about 400,000 primary follicles (immature ova) in her ovaries. She does not produce any new ova during her life time, however fewer than 500 ova will actually be released.

 The primary follicle function is to prepare a single ovum (egg) for release into part of the reproductive system where it can be fertilized.

 Under the influence of FSH, one (or more) ovum completes meiosis and increases in size as nutrients are added to the cytoplasm.

Fertilization and Implantation

Day 3 Day 2 Day 4

2 cells

Day 7 Fertilizati on

Fallopian tube

Day 1

Zygote

Day 0 Implantation

Uterine wall Ovary

Egg released by ovary

Ovulation

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 Ovulation is the release of a mature egg from the ovary into the oviduct (fallopian tube).

 Ovulation is caused by an increase in the hormone LH produced by the pituitary.

 During ovulation, the follicle ruptures, and the ovum is swept from the surface into the opening of one of the two fallopian tubes.

 Note: In females ovulation begins at puberty and usually continues until the female is in her late forties, when menopause occurs. After menopause. Follicular development no longer occurs and the female is no longer capable of bearing a child.

Oviduct or Fallopian Tubes

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 Tubes that carry the egg or embryo to the uterus  The egg moves through the fluid filled tubes, pushed along by microscopic cilia  Fertilization takes place in the upper 2/3 of the fallopian tube if sperms are present  The oviduct is 8-10 inches long and 2-3 mm wide.

 The tubes lead to the uterus, where the embryo develops into a fetus

Ectopic Pregnancy:

 occurs when implantation occurs in other areas of the reproductive tract other than the uterus.  Results in severe pain, loss of pregnancy, and possible death.

Uterus

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 Pear shaped muscular structure where the embryo develops  It contracts during labor to force the baby out of the body  It builds up a lining every month to support the developing embryo if fertilization of an egg occurs. If an egg is not fertilized the lining of the uterus is shed = menstruation

Cervix

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 The narrow structure at the bottom of the uterus  Ejaculation of sperm by the male occurs here during intercourse  It supports the uterus during pregnancy and dilates (gets wider) during birth or delivery

Vagina

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 Located at the bottom of the cervix and is connected to the uterus  Site of sexual intercourse  Also called the birth canal; this is where the baby passes as it leaves the body.

The Female Section 39-3 Reproductive System

The Female Reproductive System

Fallopian tube Fallopian tube Ovary Urinary bladder Pubic bone Urethra Vagina Uterus Cervix Rectum Vagina Ovary

The Menstrual Cycle  The menstrual cycle begins at puberty and ceases with menopause.

 The duration of the menstrual cycle is 28 days but may vary considerably and may be interrupted by pregnancy, illness, and other factors.

 The menstrual cycle occurs every 28 days in the female to prepare the uterus for implantation of the embryo if fertilization of an egg should occur.

 If an egg is not fertilized each month, it is discharged along with the lining of the uterus during the menstrual cycle.

The menstrual cycle consists of four stages:

Follicle stage (10-14 days)

 maturation of egg  secretion of hormone estrogen  uterine lining starts to thicken

Ovulation (14th day)

   shortest phase- lasts 3-4 days release of an egg egg can be fertilized 24-36 hours after ovulation in the fallopian tubes

Corpus Luteum (10-14 days)

   Estrogen is continued to be released which stimulates cell growth and tissue development in the lining of the uterus Progesterone (also called the pregnancy hormone) is secreted which continues to develop the lining of the uterus At the end of this stage the lining of the uterus is fully developed and is prepared to accept a fertilized egg

Menstruation (3-5 days)

   Occurs if fertilization of an egg does not occur The egg passes through the uterus without implantation Estrogen and progesterone levels drop

 The lining of the uterus is shed  The tissue along with blood and the unfertilized egg are sloughed off or discharged through the vagina in the last phase  Menstruation lasts 3-7 days with an average of 4 days  At the end of menstruation, a new cycle begins.

Cessation of the Cycle:

 Menopause: permanent cessation of the menstrual cycle  Pregnancy: temporary cessation of the menstrual cycle (7-9 months)

Meiosis 

Meiosis

: the process that results in the production of sex cells  Results in four monoploid cells from one diploid cell  Only occurs in sex cells  Number of chromosomes per cell is cut in half

Steps of Meiosis

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 very similar to mitosis 

2 parts of Meiosis

Meiosis I Meiosis II

Meiosis I:

first division of cell

 Interphase I  Prophase I  Metaphase I  Anaphase I  Telophase I  Cytokinesis

Meiosis II:

division of cells from first division

 Interphase II  Prophase II  Metaphase II  Anaphase II  Telophase II  Cytokinesis

Interphase:

 I: growth of cell replication of DNA to form a diad  II: very short, no replication of chromosomes

Prophase:

 chromosomes thicken and condense  nuclear membrane and nucleolus disappears  centrioles appear and spindle forms

Metaphase:

 chromosomes line up on equator  centrioles move to opposite ends of the poles  spindles attach to the chromosomes  Crossing over occurs

Crossing Over Animation

 Crossing Over

Anaphase:

 chromosomes separate at the centromere and are moved to opposite ends of the poles

Telophase:

 chromosomes reach the poles

Cytokinesis:

 2 distinct cells are formed

Meiosis Animation Online

 Meiosis I & II  Meiosis: An Interactive Animation  Meiosis  mitosis vs. meiosis

Sex determination

:

 1.

2.

Diploid cells of many organisms contain 2 types of chromosomes: Autosomes (body cells) Sex chromosomes (male and female traits)

Humans:

 23 pairs of chromosomes (46 chromosomes)  22 pairs of autosomes  1 pair of sex chromosomes

Sex chromosomes:

 X and Y  XX = female  XY = male  Male parents determines sex of offspring, female always donates an X

Sex Linkage:  Thomas Hunt Morgan: worked with Drosophila

melangaster

and demonstrated that certain traits are located on the X chromosome and do not have a corresponding Y chromosome

 Many sex linked genes are recessive. Therefore, they are expressed more frequently in males than in females.

WHY

?

Answer:

 Since the male only has one copy of the X chromosome; they are more likely to display any genetic defects. Females need both X chromosomes in order to display the defect.

 Females with one defected X chromosome are said to be carriers of the trait and is likely to produce ½ of her eggs with the recessive trait.

Examples of sex linked traits in humans:

 Hemophilia  Muscular Dystrophy  Color Blindness

Test For Color Blindness:

Good Stuff: For review!

 NOVA Online | Life's Greatest Miracle | Watch the Program Here (view as quick time)