Summary
Summary Topic 16: Reproduction
Topic 16: Reproduction: IGCSE Biology course notes which will help you study for your papers. By studying these notes I achieved a 9 - A* on my Igcse
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Seller
Follow
Content preview
TOPIC 16: REPRODUCTION16.1 ASEXUAL REPRODUCTION
→Asexual reproduction: a process resulting in the production of genetically identical offspring from one parent.
-Asexual reproduction does not involve sex cells or fertilisation.
-Only one parent is required so there is no fusion of gametes and no mixing of genetic information
-As a result, the offspring are genetically identical to the parent and to each other (clones)
i.e. BACTERIA
-Bacteria produce exact genetic copies of themselves in a type of asexual reproduction called binary fission:
i.e. PLANTS (TUBERS/BUDS)
-Plants can reproduce asexually using bulbs and tubers; these are food storage
organs from which budding can occur, producing new plants which are genetically
identical to the parent plant.
-This happens in plants which grow underground such as potatoes.
-Swellings called tubers grow on them.
-Sucrose is transported from the leaves into these underground stem tubers, where
its converted into starch and stored.
-The tubers are harvested to be used as food.
-These tubers are then planted underground where they grow a new identical plant.
i.e. PLANTS (RUNNERS)
-Some plants grow side shoots called runners that contain tiny plantlets on them
(a good example of this are strawberry plants.
-These will grow roots and develop into separate plants, again being genetically
identical to the parent plant.
Advantages & Disadvantages of Asexual Reproduction
-Specifically, in crop plants, asexual reproduction
can be advantageous as it means that a plant that
has good characteristics (high yield, disease-
resistant, hardy) can be made to reproduce
asexually and the entire crop will show the same
characteristics
, 16.2 SEXUAL REPRODUCTION
→Sexual reproduction: a process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilised egg
cell) and the production of offspring that are genetically different from each other.
→Fertilisation: the fusion of gamete nuclei, and as each gamete comes from a different parent, there is variation in the offspring
-In sexual reproduction, the parent organism produces sex cells called gametes. (i.e. egg and sperm cells)
-Two gametes join in fertilisation to form a zygote.
Gametes & Zygotes
-A gamete is a sex cell (in animals: sperm and ovum; in plants pollen nucleus and ovum)
-Gametes differ from normal cells as they contain half the number of chromosomes found in other body cells – we say they have
a haploid nucleus
-This is because they only contain one copy of each chromosome, rather than the two copies found in other body cells
-In human beings, a normal body cell contains 46 chromosomes but each gamete contains 23 chromosomes
-When the male and female gametes fuse, they become a zygote (fertilised egg cell)
-This contains the full 46 chromosomes, half of which came from the father and half from the mother – we say the zygote has a
diploid nucleus.
Advantages & Disadvantages of Sexual Reproduction
-Most crop plants reproduce sexually and this is an advantage as it means variation is increased and a genetic variant may be
produced which is better able to cope with weather changes, or produces significantly higher yield
-The disadvantage is that the variation may lead to offspring that are less successful than the parent plant at growing well or
producing a good harvest
16.3 SEXUAL REPRODUCTION IN PLANTS
-Flowers are the reproductive organ of the plant
-They usually contain both male and female reproductive parts
-Plants produce pollen which contains a nucleus inside that is the male gamete
-Unlike the male gamete in humans (sperm), pollen is not capable of locomotion (moving from one place to another)
-This means plants have to have mechanisms in place to transfer pollen from the anther to the stigma
-This process is known as pollination and there are two main mechanisms by which it occurs: transferred by insects (or other
animals like birds) or transferred by wind.
-The structure of insect and wind-pollinated flowers is slightly different as each is adapted for their specific function.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller alejandrahuartealfaro. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £4.27. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
81989 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now