V. Reproduction

We can discuss reproduction under two categories: asexual (without sex) and sexual (requiring male and female gametes). 

Asexual reproduction involves cell division by mitosis.  In mitosis, chromosomes replicate during interphase and the end result is two identical daughter cells.  For a complete review, go to the Virtual Lab section and look for the Onion Root Tip Lab.

Organisms that reproduce by mitosis include amoeba and paramecium (binary fission); starfish (regeneration), yeast (budding) and some plants by cuttings, runners, bulbs (vegetative propagation).

Sexual reproduction involves the production of gametes by meiosis.  Meiosis also includes a replication of chromosomes but two cell divisions, resulting in gametes with only half the normal number of chromosomes (monoploid).  The gametes (sperm and egg) will then join during fertilization to restore the original chromosome number (diploid).

For a detailed comparison of meiosis and mitosis you may go to the Virtual Lab section and look for Meiosis.

For a nice review of Male and Female Reproductive systems, go to the Study Site entitled Human Reproduction.

VI. Evolution

Evolution is the change in the allele frequency of gene pools.  It is also the idea that organisms today had common ancestors.

Darwin's theory of Natural Selection explains the forces of evolution:

            Over time, today's organisms descended from common ancestry.

            There is much variation within the members of a single species.

            There is an overproduction of each species.

            Overproduction and limited resources lead to competition.

            Some members have better adaptations (fitness) for survival.

Darwin did not know about genetics.  Therefore he did not know about the reason for such variation.  Modern evolutionary theory  can explain variation due to meiosis, crossing over, and mutations.

In each generation, only the most fit traits (genes) will be passed on to the next generation.  Therefore, variety (biodiversity) is essential for evolution.

For a terrific website, go to study sites and look for Evolution.

VII. Biochemistry

            You are what you eat!   Nutrients we take in are metabolized to give us everything we need to grow, repair, react, create energy.   You need to learn the role of lipids, carbohydrates, proteins, water, minerals and vitamins.  Enzyme action is particularly important.  Without enzymes, your body could not allow chemical reactions to occur!

There is a wonderful site with notes and practice questions.  See study site!

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