Reproduction Flashcards
Asexual reproduction definition
A process resulting in the production of genetically identical offspring from one parent. Mitosis
Examples of asexual reproduction
- Bacteria in a method called binary fission (they only reproduce asexually)
- 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 (plants do both sexual and asexual reproduction)
- 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
- Fungi do both asexual and sexual reproduction
Advantages of asexual reproduction
- Reproduction is completed much faster than sexual reproduction
- Species can colonise new habitats faster and more efficiently
- More time and energy efficient as there is no need to find a mate
- Population can be increased rapidly when conditions are right
- For crops, there is no need for pollination, and it means that a plant that has good characteristics (high yield, disease resistant, hardy) can be reproduced asexually and the whole crop will have these characteristics
Disadvantages of asexual reproduction
- Limited genetic variation in the population- the offspring is genetically identical (no genetic diversity)
- Disease is likely to affect the whole population as they are all genetically identical
- Population is vulnerable to changes in the habitat and may be only suited for one habitat
Sexual reproduction definition
Sexual reproduction is a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other
Fertilisation definition
Fertilisation is the fusion of the nuclei of gametes. Since each gamete comes from a different parent, there is variation in the offspring
STI definition (sexually transmitted infection)
an infection that is transmitted through sexual contact
What is a pathogen that causes an STI? And what can the infection lead to?
human immunodeficiency virus (HIV) is a pathogen that causes an STI. HIV infection may lead to AIDS
Methods of transmission of HIV
- Unprotected sex with infected person
- Drug use involving sharing needle used by infected person
- Transfusion of infected blood
- Infected mother to fetus
- Unsterilised surgical instruments
- Feeding a baby milk from an infected mother
How the spread of STI’s are controlled
- Using condoms
- Regular STI testing
- Using sterile needles
- Checking if someone has an STI before sex
- Abstinence if infected
- Limiting number of sexual partners
- Raising awareness through education programs
- Not sharing the same needles for drugs
What are gametes and how are they formed?
Gametes are sex cells (in animals: sperm and ovum; in plants: pollen and ovum). They are formed by meiosis
What is the difference between gametes and normal cells?
Gametes differ from normal cells as they containhalf the number of chromosomesfound in other body cells - the nuclei of gametes are haploid. In human beings, a normal body cell contains46 chromosomesbut each gamete contains23 chromosomes
What happens when male and female gametes fuse?
When the male and female gametes fuse, they become azygote(fertilised egg cell).
- This contains the full46 chromosomes, half of which came from the father and half from the mother - the nuclei of zygotes are diploid
Advantages of sexual reproduction
- Increases genetic variation
- The species can adapt to new environments due to variation, giving them a survival advantage
- Disease is less likely to wipe out the whole population
- For crops, variation is increasedand a genetic variant may be produced which is better able to cope with weather changes, or produces significantly higher yield
Disadvantages of sexual reproduction
- Takes time and energy to find mates
- Difficult for isolated members of the species to reproduce
- Takes a while to colonise new habitats or survival advantages, so survival of species is harder to ensure
- For crops, variation may lead to offspring that areless successfulthan the parent plant at growing well or producing a good harvest
What is the stamen? And what is the carpel?
Stamen- male reproductive organs of the plant
Carpel- Female reproductive organs of the plant
Function of anther
Produces and releases pollen (male gamete)
Function of filament
Provides support to the anther, elevates it to expose it to wind and pollinators
Function of style
A tube that connects the stigma and ovary, elevates the stigma to expose it to wind and pollinators
Function of stigma
Sticky part on top of the female part of the flower that collects pollen from the wind and pollinators
Function of ovary
Contains the ovules (female gamete)
Function of ovules
Structures inside the ovary that contain the female gametes
Sepal function
Thick leaves that protect the bud before blooming
Petal function
Vibrantly coloured in insect pollinated flowers to attract pollinators