Sci 9 Lesson 6 April 12 - Sexual Reproduction

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/