Sexual Reproduction and the Diversity of Life Chapter 7 Sexual Reproduction and the Diversity of Life Mrs. McLean – Science 300

Ways of Reproduction

The Difference Between Asexual and Sexual Asexual Reproduction – a single cell ( the mother cell) duplicates the same genetic information and becomes two daughter cells. Sexual Reproduction – genetic information from two cells is combined to form the new genetic code for a new organism.

Sexual Reproduction Types: Conjugation, Hermaphrodites, Separate Sexes Conjugation – two cells come together and exchange small pieces of their genetic information(bacteria) Hermaphrodites – organisms that create both male and female sex cells. Occurs in organisms that have restricted movement (sponges)

Sexual Reproductions continued Separate Sexes – In complex organisms specialized sex cells (sperm and egg) combine to form a zygote. Offspring are not identical to either the parent or further offspring (humans and some plants)

Fertilization

Homework Read Section 7.1, pages202-205 Do questions 1-6 on page 205

Meiosis Review The process of forming sex cells, A human body cell contains 23 pairs of chromosomes. The gametes - sperm or eggs - contain half this number of chromosomes, which is why meiosis is sometimes called 'reduction division'.

Meiosis continued Organisms that reproduce sexually contain 2 types of cells. 1) Somatic- cells that reproduce by mitosis, when cells divide each daughter cell is identical as the mother cell (skin and muscle cells 2) Reproductive- produce sex cells which only have half the number of chromosomes (haploid cell)

Parts of the Flower Draw and copy this chart into notes

The Male Parts Pollen – the male sex cells of the flower Filament - This is the stalk of the Anther. Anther - The Anthers contain pollen sacs. The sacs release pollen on to the outside of the anthers that brush against insects on entering the flowers. * The filament and the anthers are collectively known as the Stamen

The Female Parts of the Flower Egg the female sex cells of the flower Stigma Is covered in a sticky substance that the pollen grains will adhere to. Style The style raises the stigma away from the Ovary to decrease the likelihood of pollen contamination. Ovary This protects the egg and once fertilization has taken place it will become the fruit.

Homework Read section 7.3, pages208-209 Be prepared to label the parts of the cell as seen on page 210 in the textbook (study the diagram) Do questions 1-6 on page 209

Homework Read section 7.5, pages212-213 Do questions 1-4 on page 213

Answers to 7.3 Questions 1. Flowering plants contain both male and female sex cells. 2. Male sex cell (pollen) and female sex cell (eggs). 3. During reproduction, the pollen makes its way to the female egg cells. This process is called fertilization. The fertilized eggs become seeds which grow a new plant.

7.3 Answers continued 4. Once fertilized, the ovary becomes larger and grows into the fruit. 5. Seeds (b&c) have spikes that get entangled with animal fur. A & D have large surfaces that catch the wind. E has a parachute that catches the wind. 6. Since the fruit is usually appetizing, the animals eat the fruit and the seeds get dispersed.

Strategies for Increasing Food Production

Better disease resistance Better nutritional quality Improved flavour Reasons for selective breeding, crossbreeding, cloning, grafting, and genetically engineered (modified) plants Higher crop yield Better disease resistance Better nutritional quality Improved flavour Development of traits that are useful fro storage, shipping and processing

Monocultres Def’n: When large areas of agricultural land are planted with just one variety of food crop Irish Potato Famine People’s dependency can cause mass deaths or emigration Increased use of fertilizers HW- #1-3 on page 213

Answers to #1,2,3 on Page 213 1. As the world population continues to increase, food production must be increased or many people will starve. 2.Grafting allows a tree to produce a different type of fruit quickly. Selective breeding identifies plants with the most desirable traits. Since fertile land is limited, farmers can get better yields by growing grafts.

Answers continued 3. Clones produce exact duplicates of the parent plants. In grafting, a section from one plant is attached to another. The grafted plant and the host plant do ot exchange genetic information.