Upon completion of this unit you will be able to:
1. Explain the cell cycle and identify
the significant features of the G1, S and G2 phases
2. Name the stages of mitosis and
describe major events that distinguish each stage.
3. List cells that lose their mitotic
ability and those that retain this capacity.
4. Cite prominent differences between
plant and animal cells during mitosis.
5. Describe the characteristics of
a clone and explain how it is produced.
6. Compare and contrast mitosis and
meiosis.
7. Explain the importance of crossing-over
during meiosis.
8. Explain why sexually reproducing
organisms must form cells with a haploid number of chromosomes.
9. Distinguish between sexual and
asexual reproduction.
10. Cite examples of asexual reproduction
displayed by living organisms.
11. List advantages and disadvantages
of sexual and asexual reproduction.
12. Define Nondisjunction
and explain its relavance to chromosomal genetics.
13. Identify the four flower parts,
provide their functions and describe which are essential flower parts.
14. Differentiate between pollination
and fertilization.
15. List several mechanisms of pollination.
16. Discuss alternation of generation
and distinguish between sporophyte and gametophyte generations.
17. Define dioecious, monoecious and
synoecious and site examples of plants following each strategy.
18. Identify the plumule, radicle,
and cotyledon in the seed embryo.
19. Discuss the development of a fruit;
describe the different classifications of fruit.
20. Differentiate between parthenogenesis
and parthenocarpy.
21. Describe hermaphroditic animals.
22. List examples of oviparous, viviparous
and ovoviviparous animals.
23. Discuss the efficiency issues
facing animals using external and internal fertilization strategies.
24. Compare and contrast the embryo of
a seed plant with that of an oviparous animal.
25. Provide the functions of the following:
testes, testosterone, estrogen, follicle, corpus luteum, progesterone,
pituitary gland uterus, FSH, LH, ovulation.
Unit References: Text Chapters 9, 22, 27 http://www.mhhe.com/enger12
Unit 7: Mitosis/Meiosis; Sexual/Asexual
Reproduction
(how genetic information is passed)
Biological Trivia: (Objective #3)
-Average RBC lives ~120 days and there
are about 25 trillion in an adult. To maintain,
about 2.5 million new RBC's must
be produced by each second
-Nerve cells lose their capacity to replicate once they mature
-Some cells retain capacity to divide but do so only under certain circumstances:
Liver- if portion removed surgically
remaining cells will replicate themselves until liver
reaches its former size.
-About 2 trillion cell divisions
occur in an adult human every 24 hours, that's ~25 million/sec.
I. MITOSIS/MEIOSIS
(Objective #6) pg 164-171 of text
A. Mitosis - nuclear division, maintains
chromosome number unchanged
from parent
-occurs in somatic cells
-occurs in bacteria (binary
fission) and single celled animals
-daughter cells have same genetic
makeup as parent cells
-growth/ repair and maintenance
Check Out : The Cell Cycle and Mitosis Tutorial
Onion Root Tip Simulation
Interactive Mitosis Tutorial
Shockwave Mitosis
B. Meiosis pg.
174-181- nuclear division, chromosome # reduced from diploid to
haploid
(Objective #8)
-sexually reproducing organisms,
produces variability in chromosome sets
-crossing over produces greater
variability
-homologous chromosomes pair.
C. Cell Cycle
(Objective #1, 2) text pg 164-170
Interphase:
G1- Gap phase one; cell
grows, produces tRNA, mRNA, ribosomes, enzymes
S- synthesis; DNA replication,
prep for cell division
G2- Gap phase two; synthesis
of fibers needed to pull chromosomes apart
Text pgs. 166-169
Mitosis: Prophase;
chromatin becomes condensed to chromosomes
Metaphase;
chromosomes line up at equator
Anaphase; chromosomes
split at centromere and move to poles
Telophase;
new sets of chromosomes becomes enclosed by new nuclear
membrane
Cytokinesis- division of cytoplasm
*gradual and continuous process
*nerve and muscle cells come to rest in S phase
(Objective #4)
text pg 169
*Plant cells- cell plate forms
between new cells
*Animal cells - have centrioles,
cleavage furrow forms between cells
Meiosis-
(pgs 174-181 ) 2 divisions rather than one as in mitosis
(prophase I . . prophase
II. .
In mitosis all chromosome
pairs line up on equator
In meiosis homologous chromosomes line up (2 lines)
Mitosis
Meiosis
Check
Out : Botany
Online- Meiosis (Check Biology Handbook)
NCSU Meiosis Tutorial
How Cells Divide: Mitosis vs. Meiosis
Biology Hypertextbook: Meiosis and Genetic Recombination
Biology Project Meiosis Tutorial
CROSSING OVER (Objective #7)
text pg 182-183 events in Meiosis increase genetic variability
(allows page by page variability)
w/o crossover
w/ crossover
Check Out
: Crossing
Over of Chromosomes in Meiosis
Problems with Meiosis: Nondisjunction
(objective 12) ,
text pg 185-187
Downs Syndrome- autosomal nondisjunction
Kleinfelters, Turners- sex chromosome nondisjunction
Nondisjunction in autosomes rarely tolerated
II SEXUAL AND ASEXUAL REPRODUCTION
text pgs 164 (Objective
#9, 10)
A. Asexual reproduction
- **main reproductive event is mitosis, one parent (single
donor of genetic information),
end result is two genetically identical offspring
cells (daughter cells)
1. Fission- bacteria, single
celled animals, yeast, algae
-nuclear material replicates
and then organism divides
-2 identical daughter
cells produced
2. Budding- small projection
of cellular material contains DNA, grows from cell
(or organism): yeast,
hydra
-as bud grows wall develops
between bud and parent, seperation occurs, new
individual arrives
3. Fragmentation/regeneration
-new organisms formed
from pieces; anemonies, sponges
-starfish can split central
disc; Crown of Thorns (at least 1/5 central disc)
4. Sporulation- fungi, (some
plants), protozoans, bacteria
spore- reproductive cell
(mitosis), protective coat, widely dispersed. Contains
nuclear
material
-mildew, plant rusts,
smuts, difficult to destroy
5. Vegetative- plants (best known)
-production of new organisms
or portion from part of a living organism.
-plant cuttings, potatoes,
strawberries (runners, stolons), grafts (trees)
ADVANTAGES OF ASEXUAL REPRODUCTION
(Objective 11)
-simple process, one parent
involved, no waste of energy to find mate
-large numbers can be
produced
-spores can be widely
dispersed, increases chance of survival
DISADVANTAGES OF ASEXUAL REPRODUCTION
-produces clones. In
an environment that changes there is no variability to deal
w/changes
Check Out:
Asexual Reproducers
Breakthroughs in Bioscience- Cloning
B. Sexual Reproduction
pg 174 (Objective #9) - requires haploid
gametes (eggs and
sperm) that unite to produce
a zygote
-main reproductive event is
meiosis (gamete production)
1. ADVANTAGES
(Objective #11)
-introduction of variability
to zygote from two parents. Allows greater diversity and
adaptability
-care of young
2. DISADVANTAGES
-2 kinds of gametes required
-gametes must be brought
together, usually deals with large #s of gametes under
relatively "iffy" conditions
Ex. Human egg production
vs. Fish egg production; Human infertility
Check Out
:
Why Sex?
III. Plant Reproduction (Higher plants-
flowering plants) (Objective #13)
text pg 175, 474-484
1. Flower Parts
pg 507
-Pistil (female part of
flower) *essential flower part
Stigma (pollen receptor)
Style (tube from stigma to ovary)
Ovary (haploid spores or eggs)
-Stamen (male part of flower)
*essential flower part
Anther (haploid pollen
spores)
Filament (stalk on which anther resides)
Mature pollen contain
2 nuclei:
-generative
nucleus ---> sperm
-tube nucleus ---> directs growth of pollen tube
-Petals- (*non essential
flower part) protect inner reproductive organs and
attract insects
-Sepals- (*non essential
flower part) protects flowers when they are in bud stage
(Objective #14, 15)
**Pollination- transfer of pollen from
male to female
Various strategies: ~65% of
all flowering plants are insect pollinated
-grasses, wind; ferns, mosses, water; animal carriers
**Fertilization- union of egg and sperm
(Objective #17)
When dealing with stamens and pistils (and
how best to get pollen together with ovum)
there are three strategies:
Monoecious plants- both male and
female flower on same plant
Corn: male tassels (stamens
only), female silks (pistil only)
Dioecious plants- separate sexes, therefore,
separate plants
Cottonwood, honey locus,
(humans)
Synoecious plants- male and female
parts in same flower
Most "showy" flowers
ALTERNATION OF GENERATIONS
(Objective #16) text pg 475
*microspore (male, produced
by mitosis) grow into male gametophyte or stage of
life cycle that produces
pollen/sperm (meiosis)
*megaspore (female, produced by
mitosis) grow into female gametophyte or stage
of life cycle that produces
egg/ovum (meiosis)
Alternation between: **Asexual and Sexual
stages
**A haploid and a diploid
A spore producer (sporophyte)and a gamete
producer (gametophyte)
1. Mature male gametophyte ---> produces
pollen grain (1N) (releases sperm)
Female gametophyte retained
in flower and produces ovum (1N)
2. Fertilization results in an embryo
(2N zygote) that is eventually enclosed as a
seed and covered by a fruit
-fertilization double --> generative nucleus (pollen) + egg (ovum) = embryo (2N)
--> tube nucleus + polar cells = endosperm
Endosperm- nutrient material for seed;
Polar cells (2 of seven nuclei in embryo sac,
other 5 absorbed)
Seed (Objective #18) text pg 482-483- structure formed by the maturation of the ovule after fertilization
Contains: 1. sporophyte embryo
2. stored food
(endosperm)
**Fruit is a mature ovary that surrounds and protects seed
Seed Coat- protective
Cotyledon- food storage
Radicle- root origin
Plumule- shoot
Bean Seed (dicot)
Fruits (Objective
#19) text pg 482- ovary wall thickens
and becomes pericarp
*Simple fruits- single pistil w/
one to many ovum
Fleshy pericarp
Simple ovary, one seed (drupe)-
peach, plum, cherry
Compound ovary, w/many seeds
(berry)- orange, tomato, grape
Compound ovary, w/many seeds
seperated into wedges (hisperidium)- orange
Compound ovary, flesh from
recepticle (pome)- apple, pear
Dry pericarp
usually simple ovary that
splits in various ways; milkweed, beans, peas,
sunflower, grains
*Compound fruits- develop from
groups of individual ovaries
-aggregate fruits- ovaries
from single flower (blackberries, strawberries, raspberries)
-multiple fruit- ovaries from
separate flowers clustered together (pineapple)
B. Animal Reproduction
pg 175, 596-608 (chapter 27)
Male- spermatogenesis (testes,
sperm) testosterone
Female- oogenesis (ovary, egg)
estrogen
Various Strategies- some involve great
expenditures of energy just to find a mate!
1. Hermaphroditism
(Objective #21) - organism contains both male and female parts
self-fertilization (rare)-
Hydra
Cross-fertilization- must
find mate despite having both sexes (earthworms)
2. Parthenogenesis
(Objective #20)- unfertilized eggs develop into adults
Bees- haploid males (chromosome
# determines sex)
Aphids-
Parthenocarpy (plants)-
fruit development without fertilization
(Objectives #22, 23)
3. External Fertilization- eggs
deposited, sperm shed over eggs. Least efficient
Numbers game. Little
control over fate of eggs
Oviparous- "egg producing"- eggs released, fertilization and development external
4. Internal Fertilization- sperm deposited inside receptor of female
Ovoviviparous- "live egg
producing"
eggs fertilized
and develop within female, nourishment in egg,
hatch within
parent or immediately
after laying. (pit vipers, guppies,
birds)
Viviparous- "alive producing"-
eggs develop within female body, nutritional aid from
mother (placentals).
(Objective #25)
text pg 599-608
Hormonal Control of Human Reproduction
Female: Anterior lobe of pituitary gland
---> FSH (Follicle Stimulating Hormone).
One follicle per menstral
cycle. Follicle contains egg.
Follicle produces estrogen
effects hypothalamus and pituitary
so that FSH production
slows and LH (Leutinizing
Hormone) released by pituitary
LH causes follicle to mature
and rupture (ovulation)
Corpus Luteum (ruptured
follicle) makes progesterone, helps prepare uterus
for pregnancy
If fertilization
No fertilization
9 months ---> baby
progesterone drops, menstral flow, repeat cycle
Feedback Inhibitors
"pill"- estrogen, inhibits FSH
release, therefore, follicle never stimulated to form
progesterone, reduces amount of LH, therefore, prevents ovulation
OBJECTIVE #24
Oviparous
embryo Seed embryo
production large #s
large #s depending on species
protection little if any seed coat
development begins upon fertilization
begins at fertilization but experiences a
continues
through birth dormant period prior to germination
dispersal little, usually stay
in large, winds and animals contribute to
one spot
to develop wide dispersal of seeds away from parent.