Metabolism refers to all the chemical reactions that occur within living organisms. It includes both anabolic (building up) and catabolic (breaking down) processes.

Key metabolic processes:

• Carbohydrate synthesis and breakdown
• Protein synthesis and amino acid production
• Lipid synthesis

Definition: Metabolism is the sum of all biochemical reactions in an organism.

Variation describes differences in characteristics between individuals in a population. Sources of variation include:

• Genetic differences (inherited traits)
• Environmental factors
• Combinations of genes and environment

Highlight: Mutations are changes in DNA sequences that can lead to new traits, driving evolution when beneficial.

Meiosis is a type of cell division that produces gametes (sex cells) with half the normal number of chromosomes. Key points:

• DNA replicates before cell division
• Results in four genetically different daughter cells
• Restores full chromosome number during fertilization

Vocabulary:

• Gamete: Specialized sex cell formed by meiosis
• Chromosome: Structure made of DNA found in cell nuclei
• Allele: Different form of the same gene

DNA (deoxyribonucleic acid) is the genetic material found in cell nuclei. It has a double helix structure composed of two strands.

Key genetic concepts:

• Genes are sections of DNA coding for specific proteins
• The genome is an organism's complete set of genetic material
• Genotype is the genetic makeup, while phenotype is the observable traits

Definition: A gene is a section of DNA that codes for a specific protein.

Sexual reproduction involves:

• Two parents contributing genetic material
• Production of gametes through meiosis
• Fusion of male and female gametes (fertilization)

In animals, sperm fertilizes an egg. In plants, pollen fertilizes an ovule.

Selective breeding is the process of choosing organisms with desired traits to produce offspring.

Benefits:

• Disease-resistant crops
• Increased meat/milk production in livestock
• Desired traits in domesticated animals

Example: Dogs have been selectively bred for traits like gentleness and specific physical characteristics.

Risks:

• Reduced genetic diversity
• Increased susceptibility to diseases
• Inherited defects due to inbreeding

Highlight: While selective breeding can produce desired traits, it can also lead to health issues in some breeds due to limited genetic diversity.

Genetic engineering is the process of modifying an organism's genome by inserting genes from another organism. This allows the creation of organisms with desired traits.

Key steps in genetic engineering:

1. Isolate desired gene
2. Insert gene into a vector
3. Transfer vector into target cell
4. Allow modified organism to develop

Highlight: Genetic engineering has potential benefits like curing inherited diseases and improving crop yields, but also carries risks like gene transfer to wild species.

Cloning produces genetically identical organisms through asexual reproduction methods. Common cloning techniques include:

• Tissue culture for plants
• Embryo transplants for animals
• Adult cell nuclear transfer (e.g. Dolly the sheep)

Example: Tissue culture involves growing new plants from small groups of plant cells, which is useful for preserving rare species.

Vocabulary: A clone is an organism that is genetically identical to its parent.