Top 25 Topics to revise for your IGCSE Biology Exam in 2024 (part 2)

Summary

This IGCSE Biology transcript outlines essential topics for study, including the structure and function of neurons in reflex arcs, the regulation of blood glucose and body temperature, and plant tropic responses. It emphasizes key genetic concepts such as protein synthesis and insulin production via genetic engineering, as well as reproductive processes like pollination and human fertilization. Additionally, it covers ecological principles such as energy flow in food chains, the nitrogen cycle, population dynamics, and environmental issues like global warming and eutrophication, highlighting the importance of conservation efforts for natural resources.

Takeaways

• 🧠 Understand the neurons involved in the reflex arc and synapse.
• 🩸 Learn about the control of blood glucose levels and body temperature.
• 🌱 Explore tropic responses in plants and the role of hormones.
• 🔬 Study the process of protein synthesis and the production of insulin through genetic engineering.
• 🌸 Examine the processes of pollination and fertilization in plants and humans.
• ♀️ Understand the role of different hormones in regulating the menstrual cycle.
• 🌍 Recognize the importance of natural selection in biology.
• ⚡ Learn about the flow of energy in food chains and the role of bacteria in ecosystems.
• 📈 Study the population growth curve and the impacts of global warming.
• 🌳 Understand the events leading to eutrophication and the importance of forest and fish stock conservation.

Q & A

What are the main components of the reflex arc?

The main components of the reflex arc include sensory neurons, interneurons, and motor neurons. These components work together to process a stimulus and produce a quick response.

How is blood glucose level controlled in the body?

Blood glucose levels are regulated primarily by insulin and glucagon, hormones produced by the pancreas. Insulin lowers blood glucose levels by facilitating the uptake of glucose by cells, while glucagon raises levels by promoting the release of glucose from the liver.

What role do auxins play in plant tropic responses?

Auxins are plant hormones that regulate growth in response to environmental stimuli, such as light (phototropism) and gravity (gravitropism). They cause differential growth rates on different sides of the plant, directing its growth toward the stimulus.

What is the process of protein synthesis?

Protein synthesis involves two main steps: transcription, where DNA is transcribed into mRNA, and translation, where ribosomes read the mRNA sequence and assemble amino acids into a polypeptide chain to form a protein.

How is insulin produced through genetic engineering?

Insulin is produced through genetic engineering by inserting the human insulin gene into bacterial plasmids. The bacteria then produce insulin as they grow, which can be harvested and purified for medical use.

What occurs during pollination and fertilization in plants?

Pollination is the transfer of pollen from the male anther to the female stigma. Fertilization occurs when a pollen grain germinates, and the sperm cell travels down the style to fertilize the ovule, forming a zygote.

What are the different hormones involved in the menstrual cycle?

The key hormones involved in the menstrual cycle include estrogen and progesterone, which regulate the menstrual phases, and luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which control ovulation and follicle development.

What is natural selection?

Natural selection is a process in which organisms better adapted to their environment tend to survive and reproduce more successfully than others, leading to evolutionary changes in species over time.

How does energy flow through a food chain?

Energy flows through a food chain from producers (like plants) to primary consumers (herbivores), then to secondary consumers (carnivores) and so on. Energy is lost at each trophic level due to metabolic processes, heat, and waste.

What is eutrophication, and what causes it?

Eutrophication is the enrichment of water bodies with nutrients, often due to runoff from fertilizers. It leads to excessive growth of algae, which can deplete oxygen levels and harm aquatic life.