Study Notes
Variation and evolution are key concepts in biology that explain how species change over time and adapt to their environments. Reproduction — the production of new organisms, ensuring species continuity. Example: Plants and animals reproduce to pass on genetic information. Asexual reproduction — involves one parent and produces genetically identical offspring. Example: Bacteria reproduce through binary fission. Sexual reproduction — involves two parents and produces genetically diverse offspring. Example: Humans reproduce sexually, combining genetic material from both parents. Meiosis — a type of cell division that reduces chromosome number by half, creating genetic diversity. Example: Meiosis produces gametes like sperm and eggs. DNA — the molecule that contains genetic information in a double helix structure. Example: Human DNA is organized into 23 pairs of chromosomes. Gene — a segment of DNA that codes for a specific protein. Example: A gene might determine eye color. Mutation — a change in the DNA sequence that can affect protein function. Example: Mutations can lead to genetic disorders like cystic fibrosis. Natural selection — the process where organisms better adapted to their environment tend to survive and reproduce. Example: Giraffes with longer necks survive better when food is scarce. Speciation — the formation of new and distinct species in the course of evolution. Example: Physical barriers can lead to speciation by separating populations.
Exam Tips
Key Definitions to Remember
- Asexual reproduction: One parent, identical offspring
- Sexual reproduction: Two parents, diverse offspring
- Meiosis: Cell division reducing chromosome number
- Mutation: Change in DNA sequence
- Natural selection: Survival of the fittest
Common Confusions
- Confusing meiosis with mitosis
- Misunderstanding the role of mutations in evolution
Typical Exam Questions
- What is the purpose of meiosis? To halve the number of chromosomes in sex cells
- How does natural selection affect a population? It increases the frequency of advantageous traits
- What is the chance of a blue-eyed child from two brown-eyed parents (Bb)? 25%
What Examiners Usually Test
- Understanding of genetic variation and its causes
- Ability to explain the process of natural selection
- Knowledge of how mutations can lead to genetic disorders