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- AKA mitotic cell division or asexual reproduction- Chromosomes of parent cell doubles
- Cell splits in half
- New cells are identical to parent cells- Happens in regular repetitive manner- Is how single-celled organisms reproduce
- In multicellular organisms is used in growth, regeneration and healing
Mitosis in Animal Cells
- Nucleus of cell contains “blueprint”
- In cells DNA is a mass of twisted threads called chromatin
- During mitosis chromatin shortens and turns into small rod-like structures
Each organism has a certain number of chromosomes in its body cells
46 48
20
8
What do youCall a fly without wings?
Steps of Mitosis
Mitosis happens pretty fast. About 1 hour to complete a division then 16 to 20 hrs resting
Typically happens in unspecialized cells. In humans happens a lot in skin and bone marrow.
1. Resting Phase
- Time between cell divisions- The cell is growing
- More organelles, proteins, etc are being made
- Nucleus can be easily seen- By end chromosomes are replicating ( copying)
2. (Prophase) - Chromosomes become visible- Start looking like double strands
3. Metaphase
- Chromosomes line up in middle- Getting ready to split apart
4. Anaphase
- Separated copies of chromosomes migrate to opposite poles of cell- One complete copy goes to each end
5. Telophase- Cytoplasm starts to pinch in
- By end chromosomes will start looking thread-like again
- Two identical cells will be made
Mitosis in Plants
What Causes Mitosis?
1. Cell grows big and divides
2. Uncontrolled mitotic division is
CANCER-Very rapid growth
-Each cancer cell produces more cancer cells
Asexual Reproduction
- A new organism is made from a cell or cells of a SINGLE parent organism
- No special reproductive cells or organs are used
- New organism looks like original
- Offspring are genetically identical to parent
-Results in large number of offspring in short period of time
Binary Fission
- Used by unicelluar organisms (bacteria, protists)
- Mitosis results in 2 identical cells
Under favorable conditions bacteria can divide every 20 minutes
Budding in Hydra
Bud forming
- Parent divides unevenly- Bud can break off and form a new individual
- hydra, yeast, and someworms
Regeneration in Planaria-organism regrows lost body parts
-more common in simple organisms
- starfish, earthworm, planaria, and hydra
Sporulation- Usually found in fungi, algae and some protozoa
GraftingGrafting
Sexual Reproduction
- 2 Parents
- New organism is not genetically identical to parent- Advantages:
1. New individual has variations that may make it better suited for environmental changes
2. New individuals may move into new environments
Nova chapter 1: Meiosis
What are the two sexiest animals?
Body cells - All cells in an organism except except the sex cells- Contain a certain number of chromosomes
- Humans have 46 chromosomes in their body cells
Diploid Chromosome Number(2n) - Body cells
- Chromosomes found in pairs with similar structure
This chromosome came from mom
This chromosome came from dad
- The pairs are called homologous chromosomes- One came from mom, other from
dad- Each carries genes for same trait
Gametes
- Specialized sex cells produced in sex organs- Contain genetic material of mom (egg) and dad
(sperm)
- Have monoploid chromosome number (n)
- ½ the number of chromosomes of body cells - 23 chromosomes in humans
Fertilization - The fusion of the nuclei of sperm and egg
Zygote - Single cell produced when gametes fuse
- This new cell will undergo mitoticmitotic division to produce new cells that are identical to the first
Meiosis - Cell division in which gametes receive only ½ the number of chromosomes that the parent has- Number of chromosomes is reduced
- Cell divides TWICE but chromosomes only replicatereplicate once - Results in four daughter cells
Stages of Meiosis
1. - Chromosomes have already replicated-
Synapsis - Homologous chromosomes line up together in nucleus- The pairs of chromosomes
are called tetrads
Crossing OverCrossing Over- Exchange of segments between homologous chromosomes- Allows for increase variationvariation
2. - Tetrads line up a equator of cell
3.-Disjunction occurs – homologous chromosomes separate and move to opposite ends of cell - Each new cell has only half of the info
that it originally had but two copies of the half
4. - Cytoplasm splits making two daughter cells
5. - Double stranded chromosomes line up in middle of cell
6. - Chromosomes separate becoming single strands- Chromosomes move to opposite ends
7. -Cytoplasm divides again
- New cells now have monoploid number of chromosomes ( ½ what the original had )
MitosisMitosis MeiosisMeiosis
Comparison of Mitosis and Meiosis
Growth and Asexual Growth and Asexual ReproductionReproduction
Sexual ReproductionSexual Reproduction Gamete FormationGamete Formation
No Crossing OverNo Crossing Over ( no genetic variation)( no genetic variation)
Crossing over occurs Crossing over occurs (provides for genetic (provides for genetic
variation)variation)
Cells Divide OnceCells Divide Once Cells Divide TwiceCells Divide Twice
Parents and offspring Parents and offspring IdenticalIdentical
Offspring genetically Offspring genetically different from parentsdifferent from parents
Results in 2n Results in 2n chromosome chromosome numbernumber
Results in n Results in n chromosome chromosome numbernumber
Advantages to Sexual Reproduction
1. Increased variation variation increases possibility that organism will be able to adaptadapt to changes in the environment
2.
Variations may allow organisms to move into new environments
3. Make the population more varied
Sexual Reproduction in Animals - Usually involves two sexes – male and
female
Gonads - Specialized organs where gametes developOvaries - Found in
females- Produce egg (ova) – (n)
Testes - Found in males
- Produce sperm (n)
Nova chapter 2: The eggs journey Stop 440
Hermaphrodites - Contain both ovaries and testes
- Found in slow moving organisms
- Animals rarely self fertilize
- When they come in contact with other animal they both exchange sperm and eggs
Gametogenesis
- Process of making gametes in the gonads
Oogenesis - Making of egg in ovary
Only a limited number of eggs are able to be produced by a female
By birth this has already happened
This won’t happen until puberty
Contains extra yolk
These are all dud’s
Spermatogenesis
- Making of sperm in testes
- Makes four sperm each with the n chromosome number
Egg Sperm
RoundRound TadpoleTadpole
Non-motileNon-motile MotileMotile
Larger than Larger than spermsperm
Smaller than eggSmaller than egg
n number of n number of chromosomeschromosomes
n number of n number of chromosomeschromosomes
Has YolkHas Yolk No YolkNo Yolk
Fertilization- Fusion of sperm and egg to return cells to the 2n state
Nova chapter 3: The sperms journey
Embryonic DevelopmentCleavag
e
-- Zygote divides by mitosis and new cells continue to divide by mitosis- Number of cells greatly increasesCells actually get smaller until all the cells
are the same size as the cells of an adult of the organism
- The dividing cells are called an embryo
Study of embryo’s is called embryology!!!!
Nova chapter 3: The First two weeks
Gastrulation – embryo becomes indented
- Differentiation begins
- The three layers of the gastrula will become specialized and form specific tissues in the body
- It is thought that certain sections of DNA turn off and on allowing various tissues to have different functions
-this happens very early in a pregnancy and is why mothers should avoid drugs, alcohol and chemicals especially during the first trimester
Digestive and Respiratory systems
Muscles and Reproductive systems
Skin and nervous system
Nova chapter 5 and 6: The embryo takes shape & Messages in the genes
Growth -Cell numbers continue to increase
External Development
- In water
- Embryos get nourishment from yolk
- Fertilization takes place at certain times to insure optimal growth conditions- Parents usually don’t care for young- Lot of eggs increase chance of
some young surviving
External Development -Land
Food
-protectionGases diffuse through
Fluid sac
protection
Internal development- Some reptiles and fish give birth to live
young but egg just hatches inside motherMammals
- Born underdeveloped and cared for by mom for a time- Babies feed on moms milk
Uterus (aka womb) – where embryos develop inside females bodies until birth
Placenta
- Special structure in uterus
-mom’s blood vessels and babies blood vessels are in close contact-waste from embryo diffuse into mom’s blood -nutrients and oxygen diffuse into
embryo from mom
-embryo attaches to placenta by umbilical cord
Nova chapter 7: Feeding the Growing Fetus
Non-placental mammals
Marsupials -kangaroos and oppossum
-embryos born very young
-crawl from birth canal to pouch
Monotremes - Egg laying mammals- Duckbilled platypus-Egg has lots of yolk
- Babies feed on mom’s milk
Male Reproductive System
A. Testes - Gonads of male
-produce sperm
-produce hormone testosterone- Responsible for secondary sex characteristics in males
- Deep voice, body hair, musclesTestes drop into scrotum during last month
before birth. Occasionally they don’t drop and must be dropped surgically.
Testicular Cancer is one of the most common cancers for young men. Should be checked monthly. If a lump is found go to Drs and get it checked out.
2. Scrotum - Sac of skin outside body where testes are located
- Is outside of body wall to keep temperature slightly less than body temp
-optimum temp for sperm growth
3. Epididymis - Where sperm mature and are stored
4. Vas Deferens- Tube that upwards from teste to lower abdomen
- Tubes meet at urethra
Urethra - Passageway for elimination of urine and passageway for sperm
As sperm enter urethra, prostate gland, cowpers gland and seminal vesicles release fluid called semen
Ejaculation – involuntary muscle contractions that force sperm out through urethra
The Female Reproductive System
A. Ovaries -Gonads of female- Produce eggs
- Secrete female hormone estrogen- Responsible for secondary sex characteristics- Breast development, pelvis broadens, fat distribution- Important in menstrual cycle
-found in each side of lower abdomen
- All present at birth-during a lifetime no more than 500 will be released
- Each contains about 200,000 follicles (egg sacs)
Ovulation -as egg matures follicle surrounding it bursts and releases egg
-occurs first time at puberty and then about once a month-
- Egg can be fertilized for about 24 hrs
2. Fallopian Tubes (oviducts)
- Cilia filled tubes
- Place where egg will be fertilized
- Carries egg to the uterus
3. Uterus – thick walled, muscular pear shape organ
-fertilized egg attaches to wall and continues development
4. Cervix -Narrow neck of uterus
- Opens into birth canal (vagina)
Urethra - Tube that eliminates waste from body- Completely separate from reproductive system
Menstrual Cycle
-begins at puberty – 10 to 14 year old
- Controlled by hormones made by pituitary gland and ovary
-For most women occurs on 28 day cycle- Stops during pregnancy
- Stops completely during middle age(45-50) Menopause
Stages of Menstrual Cycle
1. Follicle Stage - Follicle stimulating hormone is secreted by the pituitary gland
-FSH causes follicles to develop
-usually only one develops- Developing follicle secretes estrogen
-uterus wall thickens with mucus and blood vessels-prepares uterus for pregnancy
- Last 10 to 14 days
2. Ovulation - High levels of estrogen in body cause pituitary to stop releasing FSH and start producing LH- LH reaches a certain level and egg is released ( ovulation ) - Around day 14
3. Corpus Luteum StageAfter ovulation LH causes the empty
follicle to fill with a mass of cells called the corpus luteum
- Corpus Luteum secretes hormone progesterone
-continues growth of uterus
- Prevents FSH from being released- No new egg will
develop- Lasts 10 to 14 days
4. Menstruation
- If fertilization does not occur
1. LH secretion decreases
2. Corpus Luteum breaks down and progesterone secretions decrease3. Thickened lining of uterus breaks down
4. Extra layers of uterus, unfertilized egg and a little blood pass out of body though vagina
- Lasts 3 to 5 days5. Amount of estrogen in body decreases-FSH secretion increases and new
follicle develops
Fertilization, Implantation, and Development
Fertilization - Sperm travels from vagina to cervix to uterus then into fallopian tubes
- If egg is present sperm and egg fuse becoming a 2n zygote
- Only one sperm can break through
- 5 to 10 days after fertilization embryo enters uterus
When Twins Marry Twins (LOOK OUT)
Sarah met Adam in college and they were married as soon as they graduated. At their wedding, Sarah’s identical twin sister, Emma met Adam’s identical twin brother, Ken, for the first time. Emma and Ken were married three months later. The couples kept in touch, and two years later, Sarah and Emma were delighted to discover they were both expecting. Emma’s baby Ken Jr. was born in October.
Now, Sarah is in labor and she’s worried about the child she’s about to deliver. “Why didn’t we think of this sooner?” she says. “Identical twins should never marry identical twins. Our baby is going to be a clone of Emma and Ken’s little boy.” Ken Jr. was not what most people would call an adorable baby. His parents were worried that his irritability and behavior might be due to a health problem.
As Adam walked to the hospital nursery to see their new baby, he thought about what Sarah had said.
* Will their child look just like his or her “double cousin,” Ken Jr.? What do you think? Explain using at least 3 principles or concepts of reproduction and genetics.
* Assuming that Sarah is correct, and the children will look identical, will they also have similar personalities, behavior, and attitudes? Explain .
Implantation -enzymes from embryo “digest” part of thickened uterus and embryo attaches to this spot
-gastrula forms three germ layers
-developing human is an embryo until up to about 8 weeks after this it is called a fetus- Corpus luteum continues to produce progesterone maintaining uterus
Nourishment of Embryo
- At first yolk nourishes embryo
Umbilical Cord - Attaches to belly button-brings blood to placenta
Placenta - Moms and babies blood vessels come in contact-where wastes and nutrients s are exchanged
- Moms blood and babys blood are not exchanged
-harmful things can pass from mom to baby- nicotine, alcohol, drugs, german measles
Amnion -Fluid filled sac that protects babyNova chapter 8: The Third Trimester 4:50
Ultrasound
http://health.howstuffworks.com/adam-200131.htm
Birth-gestation period – length of pregnancy
20 days for a Mouse
21 months for an elephant
- 9 Months for a human
When fetus is ready to be born1. Uterine muscles start rhythmic contractions2. Amniotic sac bursts (water breaks)
3. Cervix dialates (opens up)
From 1 to 2 cm to 11 to 12 cm
Which causes mammary gland to produce milk
4. Baby is force out head first (usually)
5. Umbilical Cord is tied and cut leaving navel
6. Afterbirth – contractions expel placenta and
amnion-during pregnancy progesterone and estrogen prepare breasts for nursing
-After birth pituitary gland releases prolactin
Premature Birth
Cesarean Section
How does the baby come out (funny)
Multiple Births
Fraternal Twins- 2 eggs released and fertilized
-Two people with DIFFERENT hereditary material develop
- May be a boy and a girl
Identical Twins - 1 egg fertilized
- Egg divides into two embryos
- Both are same sex and have same genetic material
Twins
How is a zygote formed?
Compare genetic content of zygote to genetic content of the body cells of parents.
Identify a developmental process involved in the change of a zygote into an embryo
Where does fetal development usually occur?
Identify two factors that can affect fetal development and explain how each factor affects fetal development.
REVIEW