Science 9

Unit A: Biological Diversity

Science InAction 9

Asexual and Sexual ReproductionSection 2.2: Pages 30-36

Lesson #4Learner OutcomesLearner Outcomes

I can I can distinguish between sexual and asexual reproduction, and identify and interpret examples of asexual and sexual reproduction in different species.

I can compare sexual and asexual reproduction, in terms of the advantages and disadvantages

Asexual Reproduction

• Involves only one parent – offspring are identical to the parent.

4 Main Types

• Binary Fission

• Budding

• Spore Production

• Vegetative ReproductionWhat type is this?

Binary Fission• Only single-celled

organisms reproduce in this way.

• The cell splits into two cells and each one is identical.

Eg. bacteria, amoeba, algae

Budding• Parent organism produces a

bud (a smaller version of itself), which eventually detaches itself from the parent and becomes a self-sufficient individual.

• Identical to the parent.

• Eg. Coral, hydra, yeast, coral

Spore Production• spores are similar

to seeds

• produced by the division of cells on the parent, not by the union of two cells

• Eg. fungi, green algae, moulds, ferns

• One parent may produce many spores, each of which will grow into a new individual, identical to its parent.

Vegetative Reproduction• is the reproduction of a plant not

involving a seed, including; cuttings, runners, suckers, tubers.

• Eg. coleus plant, spider plants, strawberries, aspen, potatoes

Parthenogenesis

• Occurs in some species of social insects, snakes and some plants

• Means “virgin birth”

• Unfertilized eggs become mature organisms

• Eg. Unfertilized ant eggs become male drones and fertilized ones become female workers and queens

Sexual Reproduction

Sexual Reproduction• Involves two individual organisms.

• The offspring that are produced from this union have a mix of characteristics, half from one parent and the other half from the other parent.

Sexual Reproduction• Does not always involve

male and female parents, but can have specialized gametes

• Gametes are reproductive cells that have only one role - to join with another gamete during reproduction

Sexual Reproduction in Animals

• In animals involves gametes.

• The male gametes are called sperm cells, and the female gametes are called egg cells (ova)

• These cells unite to form a fertilized combination of cells called a zygote

Sexual Reproduction in Animals

• This zygote will begin to divide (cleavage) into two cells and this continues to be repeated over and over resulting in the development of an embryo

• This embryo develops into a multi-cellular organism inside the female (in most mammals) or, outside (in an egg shell) in other animals

Human Reproduction

Frog Reproduction and Life Cycle

Sexual Reproduction in Plants

• involves male gametes and female gametes that join, during fertilization, to produce a zygote and then an embryo

• Most plants produce both male and female gametes, while some produce one or the other only

Plant Reproductive Parts

Roles of Plant Reproductive Parts

• Pollen contains the male gametes and is found on the stamen

• Ovules contain the female gametes and are found in the pistil

• Pollination occurs when pollen is transferred from the anther of the stamen to the stigma of the pistil

Cross Pollination

• Cross-pollination occurs when pollen from one plant is carried to the stigma of another plant by wind, water or animals (bees or butterflies)

Roles of Plant Reproductive Parts

• Cross-fertilization occurs when a grain of the pollen forms a long tube, which grows down the style into the ovary.

• The gametes unite to produce a zygote, which then develops into an embryo

Roles of Plant Reproductive Parts

• This usually happens inside a seed, which protects the embryo and provides food (cotyledon) for the embryo when growing conditions are right.

• Plants which are produced, as a result of cross-fertilization, are not identical to either plant.

How do the different types of reproduction affect variation?

Asexual Reproduction• Does not require specialized

cells to produce a new plant.

• Reproduce quickly.

• Little variation.

• Population may be wiped out quickly when the environment changes.

Sexual Reproduction• Lots of variation

within the species.

• Takes a lot of energy to reproduce.

• Reproduce small populations.

Organisms that reproduce asexually and sexually

Sponges • Most plants that produce seeds

can also reproduce asexually (cuttings, runners)

• Depending on the

environmental conditions the amount of energy varies, enabling the plant organism to control its population.

Sample Multiple Choice Questions

Q1. There are different forms of reproduction in organisms. Asexual reproduction involves only one parent. A hydra reproduces asexually when it produces a smaller version of itself by …

A. budding B. binary fission C. spore production D. vegetative reproduction

Sample Multiple Choice Questions

Q2. When a plant cutting produces a new individual, it does so without the formation of a seed. This type of asexual reproduction is called …

A. budding B. binary fission C. spore production D. vegetative reproduction

Sample Multiple Choice Questions

Q3. This diagram illustrates the parts of a flower.

The stamen is the … A. female part B. male part C. seed producing part D. zygote producing part

Sample Multiple Choice Questions

Q4. Some plants and animals can reproduce asexually and sexually. Alternating between these types of reproduction enables the organism to be …

A. identical to their parents in all aspects B. much like their parents C. very different from their parents D. identical to parent plants every other

generation

Sample Multiple Choice Questions

Q5. Sexual reproduction is very advantageous because it provides lots of …

A. identical organisms B. variation among the speciesC. energy for the species to survive D. similar copies of the parent

Multiple Choice Question Answers

1. A

2. D

3. B

4. D

5. B

Assess Your Learning

• Page 37

• Questions 1-8

Social and Environmental Context

Questions 1-2

Be prepared to do the Lab on Investigating Flower Reproductive Structures