Biology Exam Revision: Key Concepts in Physiology and Ecology
Factors Affecting Photosynthesis Rate
Point: Photosynthesis rate increases as light intensity, $\text{CO}_2$ concentration, and temperature increase—up to an optimum point.
Explanation:
- Light provides the energy for the light-dependent reactions.
- $\text{CO}_2$ is a necessary substrate for glucose synthesis (Calvin cycle).
- Temperature affects the activity of enzymes within the chloroplasts.
Example: In experiments, the rate of oxygen release (or $\text{CO}_2$ uptake) rises with light until a plateau
Comparative Analysis of Eukaryotic and Prokaryotic Cells
11a. Plant, Animal, and Microbial Cells
Plant and animal cells are eukaryotic, featuring a true nucleus and membrane-bound organelles, whereas most microbial (bacterial) cells are prokaryotic, lacking a true nucleus and typical organelles.
Plant cells possess a cellulose cell wall, chloroplasts, a large central vacuole, and plasmodesmata. Animal cells lack a cell wall and chloroplasts but contain lysosomes, centrioles, and a prominent extracellular matrix. Bacterial cells have a peptidoglycan cell
Read MoreHuman Reproduction: Stages and Systems
Human Reproduction Characteristics
Human reproduction is sexual and has two main characteristics:
- The new individual is formed from a single cell, called a zygote.
- A zygote originates from the union (fertilization) of two gametes or sex cells.
Humans have two kinds of gametes: sperm and ova. Men produce sperm, and women produce ova.
Puberty
Puberty begins in men with the first ejaculation (spermarche) and in women when the first menstruation takes place (menarche). This process is regulated by Follicle
Read MoreEvolution, Speciation and Ecology: Questions & Answers
Evolution, Speciation and Ecology Q&A
Fixism and diversity of living things (4 marks)
Question: How does Fixism explain the diversity of living things?
Answer: Fixism claims that species were created as they are now and that they do not change. Therefore, the diversity we find today is the diversity that has always existed.
Convergent evolution: similar wings in birds & butterflies (4 marks)
Question: Explain why two very different species, such as birds and butterflies, can have similar wings
Read MorePink Bollworm Management and Integrated Pest Control
Pink Bollworm: Pectinophora gossypiella
Systematic Position
- Class: Insecta
- Order: Lepidoptera
- Family: Gelechiidae
Habits and Behavior
The pink bollworm is a nocturnal insect. At night, the insect is attracted toward light. Caterpillars feed on and destroy seeds, which obstructs lint formation. The adults mate immediately after emergence.
Crop Damage and Economic Impact
The caterpillar causes the primary damage by boring into shoots, bolls, and flowers. It damages young seeds and reduces lint production,
Read MoreThe Heart, Blood Vessels, and Lymphatic Network Explained
The Cardiovascular System
The cardiovascular system is composed of the heart and blood vessels. The heart pumps blood throughout the body.
Blood flow involves several stages: Deoxygenated (used) blood returns to the heart and is ejected to the lungs for oxygenation. Oxygenated blood then returns to the heart and is ejected through the aorta to circulate throughout the body.
Related Physiological Functions
- The kidneys chemically purify the blood.
- The liver performs blood detoxification.
- In the brain, the