Grade 9 Science ­ Chapter 5.notebook

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Grade 9 Science

Unit 3: ReproductionChapter 5

Dec 30­8:03 PM

The Cell CycleThe cell cycle is the life cycle of a cell

There are three parts to the life cycle:1) Interphase: most of the cell's life is spent in interphase, in this stage, the cell carries out the functions they need to divide and prepare for reproduction ‐ these include growth, preparation, and DNA replication2) Mitosis: in this stage the cell duplicates the contents of the cells nucleus into two equal parts3) Cytokinesis: the cell separates the two nuclei and cell contents into two new daughter cells

Grade 9 Science ­ Chapter 5.notebook

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Dec 30­8:03 PM

MitosisMitosis is the process in which the contents of a cell's nucleus divide, this results in two daughter cells that are identical to the parent

There are four phases of Mitosis (cytokinesis follows these 4) :1) Prophase: the double stranded chromosomes shorten and thicken; the nuclear membrane begins to fade2) Metaphase: X‐shaped chromosomes are pulled into a single line across the middle of the cell3) Anaphase: the chromatids are pulled to opposite poles of the cell4) Telophase: the nuclear membrane forms around each set of chromosomes; the cell is ready to divide into two separate cells

Animal cell Plant cell

Activity 5­1C

Grade 9 Science ­ Chapter 5.notebook

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January 10, 2014

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Checkpoints in the Cell Cycle

Proteins in the cell check the viability of the cell at certain points in the cell cycle. This information is directed to the nucleus, which decides whether or not the cell will divide.The cell will not divide if there are not enough nutrients to support growth, DNA has not been replicated, or the DNA has been damaged!

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Asexual ReproductionIn asexual reproduction, only one parent is involved and offspring are identical to the parent. Most reproduce quickly and in large numbers

There are five types of asexual reproduction:1) Binary Fission: a single parent cell replicates its genetic material and divides into two equal parts

Ex. Amoeba and Bacteria2) Budding: part of the cell pushes outward to form an outgrowth or bud, the bud pinches off to form the new offspring identical to the parent ‐ not all buds break away!!!

Ex. Yeast, Hydra, and sponges3) Fragmentation: an organism breaks apart as a result of injury, each fragment then develops into a clone of

its parentEx. Star‐fish and Japanese Knotweed

Grade 9 Science ­ Chapter 5.notebook

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Asexual Reproduction Continued...Types of asexual reproduction continued:

4) Vegetative Reproduction: occurs when special cells, in plants and roots, divide repeatedly to form structures that will eventually develop into plants identical to the parent

Ex. Potato sprouts, Strawberry runners, and Tulip Bulbs

5) Spore Formation: a spore is a reproductive cell that grows into a new individual by mitosis, they are light in weight, rely on water, or wind to carry spores away from parent plant

Ex. Bread mould and puffballs

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Summary of Asexual Reproduction Advantages:

‐ Large # of offspring are produced quickly‐ Large colonies can form to out‐compete‐ Large # of offspring mean the species may survive when conditions change‐ Energy is not required to find a mate

Disadvantages:‐ Offspring are genetic clones, negative mutations can destroy larges numbers‐ The produced close together must compete‐ Unfavorable conditions can wipe out entire colonies

Bookwork: Questions 1, 2‐11 & 13on page 165

Grade 9 Science ­ Chapter 5.notebook

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January 10, 2014

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Core Lab Activity 5‐2B: Determining the Best Conditions for Yeast

Reproductions

Read the procedure on Pages 162‐164