sci 9 lesson 6 april 12 - sexual reproduction
TRANSCRIPT
Homework from last class:• Complete the Meiosis cut and paste worksheet
activity
• Complete 6-1B activity on p. 197
Trisomy 18 karyotye
Chapter 6 pp. 204-220
Ch. 6.2 Sexual Reproduction
Sexual ReproductionWhat is sexual reproduction?Sexual reproduction brings non-identical gametes
together to form a new organism.
Occurs in 3 stages:• Mating - the process by which gametes are
bought together at same place and sametime
• Fertilization - process by which egg and sperm join to form a new organism
• Development - the process by which an organism develops as an embryo
pp. 204 - 206
Methods of Fertilization
p. 207
External or Internal FertilizationIn order for external or internal fertilization to produce a
successfully developing embryo, certain conditions must be met:
1. The embryo must have enough nutrients.
2. The temperature must not be too cold or too hot.
• There must be enough moisture so that the embryo does not dry out.
1. The embryo must be protected from predators and items in the environment that can potentially harm it.
A dog embryo
External Fertilizationexternal fertilization: sperm and egg join outside parents’ bodies
Advantages• Very little energy required to mate• Large numbers of offspring produced• Offspring can be spread widely in
the environment - less competitionbetween each other and parents
Disadvantages• Many gametes will not survive• Many eggs will not be fertilized• Offspring are often not protected
by parents, so many of them die
pp. 208 - 209
External fertilization in frogs
Internal Fertilizationinternal fertilization: sperm and egg join inside parents,
embryo is nourished inside mother
Advantages• Embryo protected from predators• Offspring more likely to survive,
as many species will protect theirthem while they mature
Disadvantages• Much more energy required to find mate• Fewer zygotes produced, resulting in
less offspring• More energy required to raise and care
for offspring p. 210 - 211
Internal fertilization in sea turtles
PollinationPollination: transfer of male gametes (pollen) from male
reproductive parts of a plant to the female reproductive parts of a plant (ovules)
• A form of internal fertilization in plants.• Pollen can be carried by wind or other organisms.
pp. 212 - 214
Stamen: male
reproductive organ Pistil:
female reproductiv
e organ
Video – “Life’s Greatest Miracle”
8
Embryonic development: the early development of an organism(the first 2 months after fertilization in humans)
Stages• End of the first week - ball of cells
called morula• End of second week - hollow ball
called a blastula▫ Cells at this stage are stem cells,
and have the ability to developinto any kind of cell
• In the next stage the embryo isknown as a gastrula and develops 3 layers:
ectoderm (skin, nerves)mesoderm (muscles, bones)endoderm (lungs, liver, digestive system lining)
Embryonic Development
pp. 216 - 217
Fetal DevelopmentDifferentiation: the process where cell layers form the
organs and tissues of a baby; divided into 3 trimesters.
First Trimester (0-12 weeks)• Organ systems begin to develop and form.
Bone cells form.
Second Trimester (12-24 weeks)• Rapid growth from 12-16 weeks.
Third Trimester (24+ weeks)• Continued growth, especially of brain. Fat
begins to deposit at 32 weeks to keep fetus warm at birth.
pp. 218 - 219
Sexual Reproduction:Advantages and Disadvantages
p. 220
Homework for next class:• Complete Sexual Reproduction crossword puzzle• Complete Check Your Understanding Qs on p.
223:#s 1, 2, 6, 13, 14, 15, 16
• Read over class notes and check class bloghttp://www.msoonscience.blogspot.com
Works CitedImages taken from the following sources:http://www.genetics.com.au/factsheet/fs30.asphttp://idle.slashdot.org/story/09/02/12/1647241/Zoo-Offers-Erotic-Tour-For-
Valentines-Dayhttp://www.emailvariety.com/tag/dolphin/http://www.turtles.org/i3404006.jpghttp://www.teachersdomain.org/asset/oer08_img_flowerimage/http://mydcdoctor.com/custom_content/c_137923_first_trimester.htmlhttp://ethics.davidson.edu/index.php/2010/02/the-moral-status-of-human-
embryos/