Human 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
Fundamentals of Genetics, DNA and Biotechnology
Genotype and Phenotype
Genotype: genetic constitution of an individual character or referring to a whole set of genes (e.g., AA, Aa).
Phenotype: external expression of the genotype. The phenotype is the property that presents in the individual (e.g., yellow, green).
Alleles: each of the variants of a gene. For each gene, the individual has a pair of alleles, which are commonly represented with a letter: A (dominant), a (recessive).
Heterozygous: an individual who carries two different alleles (e.g.,
Read MoreHuman Anatomy: Systems, Chemistry, and Cell Biology
Organ Systems and Their Functions
| System | Major Function |
|---|---|
| Integumentary | Protects the body and regulates temperature (skin, hair, nails). |
| Skeletal | Supports the body, stores minerals, and produces blood cells. |
| Muscular | Responsible for movement and posture. |
| Nervous | Fast communication and control of body responses. |
| Endocrine | Hormone secretion for internal regulation. |
| Cardiovascular | Transports nutrients, gases, and wastes (heart, blood vessels). |
| Lymphatic | Immune response and fluid balance (lymph nodes, spleen). |
| Respiratory | Facilitates |