🧬 Types of Reproduction
Reproduction is the process of making more of the same kind of organism. There are two
main types of reproduction:
Asexual reproduction - involves one parent
Sexual reproduction - involves two parents
🔄 Asexual Reproduction
Asexual reproduction is a process resulting in the production of genetically identical
offspring from one parent.
Key Characteristics
Occurs with just one parent
No mixing of genetic information
Offspring are genetically identical to the parent and each other (clones)
Examples
Binary fission - bacterial cells produce exact genetic copies
Potato plants - new plants develop from buds/eyes of tuber
Haploid spores in fungi - fungi produce lightweight haploid spores through
asexual reproduction that can travel through air/water, with examples like
bread mold, mushrooms, and yeasts that grow directly into new organisms
without fertilization
Advantages and Disadvantages
Advantages
Disadvantages
Faster reproduction - no mate needed
No genetic diversity - population cannot
Consistent offspring - well-suited to
Vulnerable to disease - one disease
stable environment
Energy efficient - only one parent
needed
adapt to changes
affects entire population
💑 Sexual Reproduction
Sexual reproduction involves the fusion of nuclei of two gametes to form a zygote,
producing offspring that are genetically different.
Key Terms
Gametes - sex cells (sperm and ovum in animals, pollen nucleus and ovum in
plants)
Fertilization - fusion of gamete nuclei
Zygote - fertilized egg cell
Chromosome Numbers
Gametes have haploid nuclei (half chromosome number)
Human gametes contain 23 chromosomes
Zygote has diploid nucleus (full chromosome number)
Human zygote contains 46 chromosomes
Memory tip: Haploid starts with H like Half, Diploid starts with D like Double
Advantages and Disadvantages
Advantages
Disadvantages
Increased genetic diversity - adaptable
Requires two gametes - time/energy to
Less vulnerable to disease
Slower process - lower reproduction
to environment
find mate
🌸 Sexual Reproduction in Plants
speed
Flower Structure
Male Parts (Stamen)
Female Parts (Carpel)
Anther - contains pollen (male sex cells)
Stigma - sticky surface that catches pollen
Filament - supports anther
Style - links stigma to ovary
Ovary - produces ovum (female sex cell)
Ovule - contains female sex cells
Additional Structures
Sepal - protects unopened flower
Petals - brightly colored to attract insects
🐝 Pollination Methods
Insect-Pollinated Flowers
Feature
Adaptation
Petals
Large and bright to attract insects
Pollen
Moderate amount,
large/heavy/sticky/spiky to stick to
insects
Scent/Nectar
Present to attract insects
Stigma
Sticky and inside flower
Anther
Inside flower, firmly attached
Wind-Pollinated Flowers
Feature
Adaptation
Petals
Small and dull
Pollen
Large amounts, smooth/small/light to
blow in wind
Scent/Nectar
Absent
Stigma
Feathery and outside flower
Anther
Outside flower, swinging loosely
Types of Pollination
Self-pollination - pollen transferred to stigma of same flower or different
flower on same plant
Cross-pollination - pollen transferred to stigma of flower on different plant of
same species
Effects on Population
Self-pollination - reduces genetic variation, limits adaptation ability
Cross-pollination - increases genetic variation but relies on pollinators
🌱 Fertilization Process
1. Pollen grain lands on stigma
2. Pollen tube grows down style into ovule
3. Pollen nucleus moves down pollen tube
4. Pollen nucleus fuses with ovum nucleus
5. Zygote forms and develops into seed
6. Ovary wall develops into fruit
🌿 Germination
Germination is the beginning of seed growth
Essential Requirements
1. Water - causes seed expansion and activates enzymes
2. Oxygen - needed for respiration to release energy
3. Suitable temperature - increases rate of enzyme reactions
Germination Experiment Setup
Test Tube
Condition
Result
A
Dry cotton wool (no water)
No germination
B
All factors present (control)
Seeds germinated
C
Oil blocking oxygen
No germination
D
In fridge at 4°C (no
warmth)
No germination