Y10 Sc. Us and Them Lesson 6: Sexual and Asexual Reproduction
Specific Learning Outcomes
- Define reproduction
- Differentiate between sexual and asexual reproduction in plants and animals
- Investigate plant propagation by asexual (vegetative) means
Open this powerpoint presentation on Asexual and Sexual reproduction and the following links: Source 1 Source 2 to help you carry out the tasks set below.
Copy and paste the tasks to your Us and Them file in your Science website.
Task 1: You will encounter the terms listed below in this lesson. Find their meanings
- Asexual reproduction - Formation of a new individual cell if a single parent. This process does not involve sex cells or gametes.
- Sexual reproduction - Involves the fusing of the gametes from 2 parents to form offspring.
- Clones - Every new organism produced is genetically identical to the parent cell.
- Stolons or runners - Horizontal, above the ground stems which roots can start to grow from e.g. strawberries.
- Rhizomes - An underground runner that gives rise to new plants e.g ginger, iris, lilies.
- Bulbs - Underground stems that divide by mitosis allowing many new plants to form e.g onion, garlic
- Tubers - Underground storage stem from which new plants can grow after a dormant seed e.g potatoes
- Corm - A bulb like but solid fleshy underground stem e.g taro
- Budding - Offspring developing as growth on the body of plant e.g. jellyfish
- Fragmentation - Parts of a plant will eventually break off and these parts will then grow new plants. e.g. aloe vera
- Regeneration - If a piece of parent is detached, it can grow and develop into a completely new individual eg starfish
- Artificial propagation - Producing new plants asexually by methods which humans have invented.
Task 2
- Describe asexual reproduction - Asexual reproduction is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the sex cells of gametes.
- Describe sexual reproduction - Sexual reproduction is a form of reproduction where two morphologically distinct types of specialized reproductive cells called gametes fuse together, involving a female's large ovum (or egg) and a male's smaller sperm
- List the advantages and disadvantages of asexual reproduction - Advantages : It guarantees reproduction. It can create individuals rapidly and in large quantities and keep its desired traits. Bypassing the sexual process can help a plant in times of dryness since motile sperm require water to fertilise the egg. Plants with the desired characteristics can be cloned for economic reasons. Vigorous regrowth after disturbance. Disadvantages : An asexual reproduction population tends to be genetically static (No variation). These populations are at an increased risk of devastating epidemics and population crashes. If something goes wrong, the whole population can be terminated.
- List the advantages and disadvantages of sexual reproduction - Advantages : Characteristics are inherited from 2 parents. This produces variation in the offspring. In a changing environment this gives a good chance of at least a few to survive eg diseases, climate change etc. Bad mutations can also be weeded out. Seeds/fruits are formed – allows for long distance dispersal. Disadvantages : Too much variation prevents close adaptation to any given environment. Producing large number of gametes is wasteful since a lot of them will die in stressful environments.
- What is the advantage of having both asexual and sexual reproduction available to a species? - If there is only one parent available then it can reproduce asexually.
f. How could cloning be an advantage to someone like a horse breeder? - A horse breeder could use cloning to breed specific types of horses. You could clone a winner horse and the clones will be all winners because they are exactly the same.
Task 3: Open the worksheet here to help you with this task. The powerpoint above is also a good help.
Give examples of asexual reproduction. You must include the description and specific example/s of organisms that carry such type of asexual reproduction. Copy the table below and paste to your site. (Make at least 6 rows). An example has been done for you .
Name of organism
|
Type of Asexual reproduction
|
Description of reproductive method
|
Number of parents involved
|
Bacteria
|
Binary fission
|
A bacterium splits into 2
|
1
|
Starfish
|
Cutting
|
A part of the starfish can be cut off and will grow into another species
|
1
|
Paramcemium
|
Fission
|
A paramecium splits into two a becomes two new cells.
|
1
|
Spider plant
|
Stolons/runners
|
Horizontal underground stems
|
1
|
Aloe vera
|
Fragmentation
|
Part breaks off plant and continues to grow into a new plant
|
1
|
Jellyfish
|
Budding
|
Offspring develop as a growth on the body of the parent
|
1
|
Task 4: Open here to view the task. Your teacher will provide you with a photocopy of the worksheet.
Task 5: Comparing sexual and asexual reproduction
5a.
- Fill in the table that compares sexual and asexual reproduction
Characteristics
|
Sexual reproduction
|
Asexual reproduction
|
Number of Parents
|
2 parents
|
1 parent
|
Gametes involved
| ||
How offspring compares with parents
|
If a daughter is produced then the daughter will have the father's gene. A son would get the mother’s genes.
|
Identical/Clone to the parent
|
How offspring compares with each other
|
Different
|
Identical to the parent
|
5b.
1) SEXUAL reproduction, the good, the bad!
Advantages of SEXUAL reproduction:
· Allows for v___________ in o___________ since two parents are involved.
· Allows for a large range of g________ within the s__________
· S_________ produced can be dispersed over l_________ areas.
· Harmful mutations can be weeded out by variations.
Disadvantages of sexual reproduction
· Requires special environmental climate
· Smaller number of offspring produced
· Requires genes from two different parents
· Production of many gametes can be wasteful
2) ASEXUAL reproduction, the good, the bad!
Advantages of ASEXUAL reproduction:
· Only one parent involved
· Less number of offspring can be produced at one time
· Offspring have the same gene characteristics as the parent.
Disadvantages of asexual reproduction:
· Offspring identical to parents
· Vulnerable to damage because all offspring are genetically identical.
· L_________ range of adaptations to suit a changing environment.
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