HomeBiologyB3: Reproduction and InheritanceB3.1 Sexual Reproduction in Plants

B3: Reproduction and Inheritance

B3.1 Sexual Reproduction in PlantsB3.2 Sexual Reproduction in HumansB3.3 DNA, Genes, and ChromosomesB3.4 Inheritance and PedigreesB3.5 Cell Division - Mitosis and MeiosisB3.6 Variation and Evolution
B3: Reproduction and Inheritance

Sexual Reproduction in Flowering Plants

How plants produce seeds and create genetic variation

Flowering plant with visible reproductive structures

From Flower to Seed

The journey of plant reproduction

Flower Structure
The reproductive organs of flowering plants

Flowers contain the reproductive structures that allow plants to produce seeds through sexual reproduction. Each part has a specific role in the reproduction process.

Sepals

Protective outer layer that covers the flower bud before it opens

Petals

Colorful to attract pollinators (insects, birds)

Stamen (Male Part)

Produces pollen containing male gametes

  • Anther: produces pollen grains
  • Filament: supports the anther
Carpel (Female Part)

Contains ovules (female gametes)

  • Stigma: sticky surface to catch pollen
  • Style: tube connecting stigma to ovary
  • Ovary: contains ovules (eggs)
Interactive Flower Anatomy Explorer
Click on each flower part to learn its function
Click on any part of the flower to learn its function
Pollination
Transfer of pollen from anther to stigma

Pollination is the transfer of pollen grains from the anther (male part) to the stigma (female part). This is essential for fertilization to occur.

Self-Pollination

Pollen transferred within the same flower or between flowers on the same plant

Advantage: Reliable, doesn't rely on pollinators

Disadvantage: Less genetic variation

Cross-Pollination

Pollen transferred between flowers on different plants

Advantage: Increases genetic variation

Disadvantage: Depends on pollinators or wind

Insect Pollination
  • Brightly colored petals
  • Scented flowers
  • Nectar to attract insects
  • Sticky pollen grains
  • Anthers/stigma inside flower
Wind Pollination
  • Small, dull petals or no petals
  • No scent
  • No nectar
  • Light, smooth pollen grains
  • Anthers/stigma hang outside flower
Pollination and Fertilization Simulator
Step through the process from pollen to seed
Stage 1 of 5

Before Pollination

Pollen is produced in the anthers, waiting to be transferred to a stigma

What's Happening:

  • •Anther produces pollen grains
  • •Stigma is sticky and ready to receive pollen
  • •No fertilization has occurred yet
Fertilization and Seed Formation
From pollen to seed

After pollination, fertilization occurs when the male nucleus from the pollen joins with the female nucleus in the ovule.

1
Pollen Lands on Stigma

Sticky stigma surface traps pollen grain

2
Pollen Tube Grows

Pollen grain grows a tube down through the style toward the ovary

3
Nuclei Fuse

Male nucleus travels down pollen tube and fuses with female nucleus in ovule

4
Seed Forms

Fertilized ovule develops into a seed. Ovary wall becomes fruit

Seed Dispersal
How seeds spread away from parent plant

Seeds must be dispersed (spread) away from the parent plant to reduce competition for light, water, and nutrients.

Wind Dispersal

Seeds carried by wind

Features: lightweight, wings or parachute structures (dandelion, sycamore)

Water Dispersal

Seeds float on water

Features: waterproof, buoyant (coconut, water lily)

Animal Dispersal

Seeds carried by animals

Features: hooks/spines (stick to fur) or fleshy fruits (eaten, pass through digestive system)

Seed Germination Timeline
Watch a seed grow into a seedling
Day 0

Dormant Seed

Seed is dry and inactive, waiting for the right conditions

Needs: Water, Warmth, Oxygen

Details:

  • •Seed coat protects embryo
  • •Very low metabolic activity
  • •Can remain dormant for months or years
💧
Water

Activates enzymes

🌡️
Warmth

Speeds up reactions

💨
Oxygen

For respiration

Advantages of Sexual Reproduction
Why genetic variation matters
Genetic Variation

Offspring have a mix of genes from both parents, creating unique combinations

Better Adaptation

Different individuals may be better suited to survive changing conditions (disease, drought, temperature)

Evolution

Variation provides raw material for natural selection to act on

Worked Example
Understanding seed survival rates
Question: Why does a plant produce hundreds of seeds but only a few become mature plants?

Answer:

  1. Not all seeds disperse successfully: Some land too close to parent plant where there's too much competition
  2. Wrong conditions: Seeds need specific conditions to germinate (water, warmth, oxygen). Many land in unsuitable places
  3. Eaten by animals: Many seeds are consumed by birds, insects, or mammals before germination
  4. Disease and fungi: Seeds can be attacked by pathogens before or during germination
  5. Competition: Even if a seed germinates, the seedling must compete with other plants for light, water, and nutrients
  6. Predation: Young seedlings may be eaten by herbivores

Key Concept: By producing many seeds, the plant increases the chance that at least some will survive to reproduce. This is an evolutionary strategy to ensure species survival.

Key Terms Flashcards
Test your knowledge of plant reproduction terms
Card 1 of 12
Term

Pollination

Click to reveal definition

Plant Reproduction Quiz
Question 1 of 8
Score: 01/8

Which part of the flower produces pollen?