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Reproduction and Development
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Living Environment Regents January 2008 Question 13 |
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Tuesday, 21 April 2009 10:39 |
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Option 1 – different groups of cells containing the DNA may be exposed to different environmental conditions.
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Living Environment Regents January 2008 Question 18 |
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Tuesday, 21 April 2009 10:59 |
Option 1 - A
Animals reproduce sexually. Sexual reproduction involves the fusion of two gametes, which are half cells. Sexual reproduction promotes variation because offspring inherit genes from two different parents.
In addition, when an individual produces gametes, crossing-over and independent assortment mix genes from that individual’s parent. Gametes are haploid; they contain some genes from the individual’s mother and some from the father.
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Living Environment Regents January 2008 Question 19 |
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Tuesday, 21 April 2009 11:05 |
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Option 4 – Progesterone and Estrogen
Progesterone is one of the major hormones of pregnancy and is primarily produced by the placenta. Levels of progesterone in the body rise as pregnancy progresses. Progesterone functions to inhibit the smooth muscle in the uterus from contracting and decreases prostaglandin formation, both of which allow the fetus to grow with the expanding uterus. As progesterone levels increase, other smooth muscle in the body may also be affected, such as that in the lower esophageal sphincter, which results in increased heartburn and acid reflux, especially in the later stages of pregnancy.
Estrogens also increase during pregnancy and are also produced primarily by the placenta. Among other functions, estrogens increase uterine blood flow. Prolactin, the hormone that allows for lactation postpartum, also increases throughout pregnancy, and its production is thought to be stimulated by increasing levels of estrogens.
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Living Environment Regents January 2008 Question 20 |
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Tuesday, 21 April 2009 11:11 |
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Option 2 - B
Part B is the ovary which produces gametes in the female reproductive system.
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Living Environment Regents January 2008 Question 42 |
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Wednesday, 22 April 2009 05:39 |
Option 2 – Asexual production
Asexual reproduction refers to reproduction without the fusion of gametes. Asexual reproduction is the primary form of reproduction for single-celled organisms such the archaea, bacteria, and protists. It is reproduction which does not involve meiosis, ploidy reduction, or fertilization. Only one parent is involved in asexual reproduction.
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Last Updated on Monday, 30 November 2009 15:23 |
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Living Environment Regents January 2008 Question 44 |
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Wednesday, 22 April 2009 05:44 |
- Materials can diffuse out of the mother’s capillaries into the baby’s capillaries.
- Harmful substances can diffuse/pass through the walls of capillaries.
- Molecules pass through the placenta.
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