3.1: Understand the Differences Between Sexual and Asexual Reproduction

SEXUAL REPRODUCTION: Fertilisation of two sex cells (one gamete from each parent) produced by Meiosis to form a zygote which will develop into non-identical offspring

ADVANTAGES	DISADVANTAGES
Increases variation	Time-consuming to find mating partner
Offspring can adapt to new environment	Not possible for isolated members
Susceptible to diseases due to variation (less harmful to population)

ASEXUAL REPRODUCTION: Reproduction by a single parent to produce genetically identical offspring (clones) via Mitosis

ADVANTAGES	DISADVANTAGES
Rapid increase in population	Decreases variation
Thrive in suitable environment	Vulnerable to change in environment due to inadaptability
	Less susceptible to diseases due to decreased variation (more harmful to population)

3.2: Understand that Fertilisation Involves the Fusion of a Male and Female Gamete to Produce a Zygote that Undergoes Cell Division and Develops into an Embryo

FERTILISATION: Fusion of haploid gamete to produce diploid zygote that undergoes Mitosis to develop into an Embryo

FERTILISATION

Diagram showing the Process of Fertilisation

EXPLANATION: An Egg Cell and Sperm Cell are haploid gametes, containing 23 chromosomes (half of the 46 chromosomes in a Zygote) Due to this, reproducing requires the fusion of two haploid gametes via fertilisation to form a diploid Zygote containing 46 chromosomes (half from each parent) As diploid Zygote carries a mixture of genetic information from both parents, Zygote will undergo Mitosis to develop into an embryo exhibiting genetic variation

3.3: Describe the Structure of an Insect - Pollinated and a Wind - Pollinated Flower and Explain How each is Adapted for Pollination

GENERAL STRUCTURE OF FLOWERS:

STRUCTURE	DESCRIPTION
SEPALS	Leaf-shaped structure on the outermost part of flower that protects unopened flower
PETALS	Brightly coloured leaves surrounding the reproductive part of flower to attract pollinators (e.g, insects)
STAMENS	Male part of the Flower composed of the Filament and Anther
FILAMENT	Slender stalk supporting the Anther to make it accessible to pollinators (e.g, insects)
ANTHERS	Lobes on top of the Filament that produces the male gamete of flowering plant - Pollen
PISTILS	Female part of the Flower composed of the Stigma, Style, Ovule
STIGMA	Sticky, receptive tip of the Pistil that is responsible for catching Pollen
STYLE	Tube-shaped connection between Stigma and Ovule that elevates Stigma to catch Pollen
OVULE	Structure that contains female reproductive cells which develops into Seed after fertilisation

*INSECT POLLINATED FLOWER: Flower that distributes Pollen via Insects

Diagram:

Diagram showing the Structure of Insect-Pollinated Flower

ADAPTATIONS

FEATURE	EXPLANATION
PETALS	Petals are large and brightly-coloured to attract Insect pollinators
SCENT AND NECTAR	Nectar is scented to attract Insect pollinators
NUMBER OF POLLEN GRAINS	Moderate amount of Pollen grains due to insects being efficient pollinators
POLLEN GRAINS	Pollen grains are Sticky and spiky to attach to Insect
ANTHERS	Anthers that produce Pollen are stiff and firmly attached to Filaments inside of Flower to brush against Insects
STIGMA	Stigma is sticky and inside the Flower to catch Pollen when brushed against Insect

*WIND POLLINATED FLOWER: Flower that distributes Pollen via Wind

Diagram:

Diagram showing the Structure of Wind-Pollinated Flower

ADAPTATIONS

FEATURE	EXPLANATION
PETALS	Petals are small and dull (Green or Brown coloured) as they do not need to attract insects
SCENT AND NECTAR	Nectar is not scented as they do not need to attract insects
NUMBER OF POLLEN GRAINS	Large amounts of Pollen to increase chances of pollination
POLLEN GRAINS	Pollen grains are smooth and light to be easily carried by wind
ANTHERS	Anthers that produce Pollen are loosely attached to long Filaments outside of Flower to easily release Pollen via wind
STIGMA	Stigma is feathery and outside the Flower to catch drifting Pollen grains

3.5: Practical: Understand the Conditions Needed for Seed Germination

GERMINATION: Process by which Seed emerges from period of dormancy and begins to sprout

CONDITIONS NEEDED FOR SEED GERMINATION:  

FEATURE	EXPLANATION
WATER	Water is needed to metabolically activate enzymes to break down food reserves of Starch into Glucose (source of energy for growth)
OXYGEN	Oxygen is needed for aerobic respiration to produce energy in the form of ATP for growth
WARMTH	]Optimum temperature is needed for optimal enzyme activity to facilitate survival and growth of Seed

INVESTIGATING GERMINATION

Diagram showing the Experiment to Investigate Factors that affect Germination

METHOD: s Cotton wool is placed at the bottom of four boiling tubes, each containing five Cress Seeds Each test tube is then individually set up: Test Tube A: moist cotton wool and placed in warm environment (hot water bath set at appropriate temperature) Test Tube B: dry cotton wool and placed in warm environment (hot water bath set at appropriate temperature) Test Tube C: moist cotton wool and is placed in cold environment (bucket of ice) Test Tube D: cotton wool soaked in boiled Water that is cooled off, and layered with Oil on top After all test tubes are set up, Cress Seeds in each respective test tube is allowed to adjust to new environment for a fixed number of days After a fixed number of days has passed, results are compared via: Number of Cress Seeds germinated Height of Germinated Seed

RESULT: TEST TUBE FACTOR BEING TESTED SEEDS GERMINATED A Control (All Factors Present) Yes B Water No C Temperature No D Oxygen No

3.4: Understand that the Growth of the Pollen Tube followed by Fertilisation Leads to Seed and Fruit Formation

SEED AND FRUIT FORMATION

Diagram showing Structure of Flower

EXPLANATION: Pollination involves the transfer of Pollen grain from an Anther (male plant structure) to a Stigma (female plant structure) Hence, when Pollen grain lands on Stigma, this causes a Pollen tube to grow down the Style until it reaches an Ovule within the Ovary This allows the Nucleus of Pollen grain to pass along the Pollen tube to fuse with Nucleus of Ovule via fertilisation As a result, Ovule will form a Seed, while Ovule wall forms the Seed coat, and the rest of Carpel will develop into a Fruit to carry the Seed

3.7: Understand that Plants can Reproduce Asexually by Natural Methods (illustrated by Runners) and by Artificial Methods (illustrated by Cuttings)

ASEXUAL REPRODUCTION: Reproduction by a single parent to produce genetically identical offspring (clones) via Mitosis

RUNNER (NATURAL)	CUTTINGS (ARTIFICIAL)
Diagram showing Asexual Reproduction via Runners	Diagram showing the Asexual Reproduction via Cuttings
In Runners, cells split off from parent plant to grow side branches that forms Plantlets, specialising into root hair cells As a result, Plantlets will grow roots and plant will evolve, forming plant that is genetically identical to parent plant via asexual reproduction (clone)	In Cuttings, specific plant tissue (typically undifferentiated shoot) is selected from stock plant and sterilised Tissue sample is then explanted and grown in petri dish containing sterile nutrient agar gel Explant is treated with growth hormones (auxins) to stimulate Shoot and Root development As a result, growing Shoot can be continuously divided and separated to form new samples Once Root and Shoot are developed, the cloned plant is then transferred to Soil

3.6: Understand How Germinating Seeds Utilise Food Reserves until the Seedling can Carry Out Photosynthesis

GERMINATION: Process by which Seed emerges from period of dormancy and begins to sprout

Diagram:

Diagram showing structure of Seed


STRUCTURE:

STRUCTURE	DESCRIPTION
TESTA	Tough outer seed coat that protects embryonic plant
MICROPYLE	Small pore in outer covering of seed that allows passage of Water via osmosis
COTYLEDON	Contains food stores of Starch for Seed and forms embryonic leaves
EPICOTYLE (PLUMULE)	Embryonic shoot
RADICLE	Embryonic Root

UTILISATION OF FOOD RESERVES IN SEEDS

Diagram showing Reaction that occurs in Cotyledon (food reserve)

EXPLANATION: During Germination, the absorption of Water triggers the production of plant hormones, thus stimulating the synthesis of Amylase Amylase breaks down food reserves of Starch found in Cotyledon into Glucose to be used as an energy source for growth via aerobic respiration This continues until Seedling can carry out Photosynthesis as a source of glucose for energy