1. 10-1 Cell Growth, Division, and Reproduction Key Questions: 1)What are some of the difficulties a cell faces as it increases in size? 2)How do asexual and sexual reproduction compare?

2. Limits to Cell Growth Why do cells divide rather than continue to grow indefinitely? 1.The larger a cell becomes the more demands the cell places on its DNA. –When a cell is small the info stored in DNA is able to meet all the cell’s needs. –As a cell increases in size, it usually does not make extra copies of DNA. –If the cell were to increase without limit, an info crisis would occur.

3. Limits to Cell Growth 2.The cell has more trouble moving enough nutrients and wastes across the cell membrane. –Food, Oxygen, and water enter a cell through its CM; waste products leave the same way.

4. Limits to Cell Growth The rate at which this exchange takes place depends on the surface area of the cell & the total area of the cell membrane. The rate at which food and oxygen are used up & waste products are produced depends on the cell’s volume. The ratio of surface area to volume allows us to understand why cells must divide.

5. SA/V Ratio If a cell gets too large, it would be more difficult to get sufficient amounts of oxygen & nutrients in & waste products out. This is one reason why cells do not grow too large– they divide!

6. Surface Area/Volume Ratio Surface area=length X width X number of sides (6). Volume=length X width X height SA/V Ratio=The surface area divided by the volume. What happens to volume and surface area as a cell gets larger? –The volume increases more rapidly than the surface area.This causes the ratio of surface area to volume to decrease. –Ex: Street in a town that grows in size has more traffic. If a cell gets too large, it would be more difficult to get sufficient amounts of oxygen & nutrients in & waste products out. This is one reason why cells do not grow too large– they divide!

7. Surface Area/Volume Ratio

8. Division of the Cell What is the name of the process when cells divide? What is produced in cell division? It is called cell division. Two new “daughter cells.”

9. Before Cell Division What happens before cell division? The cell replicates (copies)all of its DNA. This solves the problem of info storage because each new daughter cell gets one complete set of genetic info. Cell division also solves the problem of increasing size by reducing cell volume. Each new daughter cell has an increased SA/V ratio.

10. Cell Division and Reproduction –How do asexual and sexual reproduction compare? –The production of genetically identical offspring from a single parent is known as asexual reproduction.

11. Cell Division and Reproduction – How do asexual and sexual reproduction compare? – The production of genetically identical offspring from a single parent is known as asexual reproduction. – Offspring produced by sexual reproduction inherit some of their genetic information from each parent.

12. – In multicellular organisms, cell division leads to growth. It also enables an organism to repair and maintain its body. –In single-celled organisms, cell division is a form of reproduction. –Asexual reproduction is reproduction that involves a single parent producing an offspring. The offspring produced are, in most cases, genetically identical to the single cell that produced them. –Asexual reproduction is a simple, efficient, and effective way for an organism to produce a large number of offspring. –Both prokaryotic and eukaryotic single-celled organisms and many multicellular organisms can reproduce asexually. Asexual Reproduction

13. Sexual Reproduction –In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow. –The offspring produced inherit some genetic information from both parents. –Most animals and plants, and many single- celled organisms, reproduce sexually.

14. Comparing Sexual and Asexual Reproduction