iGCSE Biology (Combined) CAIE

This subject is broken down into 20 topics in 12 modules:

  1. Characteristics of Living Organisms 1 topics
  2. Cells 2 topics
  3. Biological Molecules 1 topics
  4. Enzymes 1 topics
  5. Plant Nutrition 1 topics
  6. Animal Nutrition 3 topics
  7. Transport 2 topics
  8. Gas Exchange and Respiration 2 topics
  9. Coordination and Response 2 topics
  10. Reproduction 3 topics
  11. Organisms and their Environment 1 topics
  12. Human Influence on Ecosystems 1 topics
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  • 12
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  • 20
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  • 7,333
    words of revision content
  • 57+
    minutes of audio lessons

This page was last modified on 28 September 2024.

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Biology (Combined)

Characteristics of Living Organisms

Characteristics of Living Organisms

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Characteristics of Living Organisms

Characteristics of Living Organisms

Movement

  • All organisms exhibit some form of movement, although this can vary widely. For example, animals can move their entire body, plants grow towards light, and single cells move structures within themselves.

Respiration

  • Respiration is a process by which energy is released from substances, usually glucose, in all living cells.
  • This energy is used to carry out various bodily functions and activities.

Sensitivity

  • Organisms must be sensitive and responsive to the environment around them. Sensitivity involves detection of and responses to changes in both the internal and external environments.
  • For example, an organism might respond to temperature changes, light levels, or the presence of certain chemicals.

Homeostasis

  • This is the ability to control internal conditions. For example, maintaining a constant body temperature or balancing water levels in the body.
  • Homeostasis helps organisms to function efficiently and survive in their specific environment.

Growth

  • Organisms increase their size and complexity through cell division and cell expansion, this process is known as growth.
  • In some organisms like mammals, growth is more rapid during earlier stages of life.
  • Some organisms like plants continue to grow throughout their life.

Reproduction

  • All organisms reproduce in order to ensure the survival of their species. This can happen asexually (single parent, offspring identical to parent) or sexually (two parents, offspring genetically different to parents).
  • Reproduction may result in the growth of new organisms or cells.

Excretion

  • Organisms need to get rid of waste products that result from metabolic reactions. This process is called excretion.
  • If these waste products were to accumulate, they could cause harm to the organism.

Nutrition

  • Lastly, all organisms require nutrition. This can be in the form of light energy (for plants), the consumption of other organisms, or the absorption of simple food molecules.
  • Essential nutrients include vitamins, minerals, water, carbohydrates, proteins, and fats.

Remember, there can be some variation in the way these characteristics are exhibited but in order to be considered a living organism, all must be present in some form or another.

Course material for Biology (Combined), module Characteristics of Living Organisms, topic Characteristics of Living Organisms

Biology (Combined)

Transport

Transport in Mammals

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Transport in Mammals

Transport Systems in Mammals

Mammals have a specialised transport system known as the circulatory system. It consists of the heart, blood vessels, and blood. This system helps in the transport of nutrients, oxygen, hormones, and waste products around the body.

The Heart

  • The heart is a muscular organ divided into four chambers: two atria and two ventricles.
  • The right side of the heart pumps deoxygenated blood to the lungs in a pathway known as the pulmonary circuit.
  • The left side of the heart receives oxygenated blood from the lungs and pumps it to the rest of the body within the systemic circuit.
  • The heart operates using a particular sequence known as the cardiac cycle, which includes the stages of systole (contraction) and diastole (relaxation).

Blood Vessels

  • There are three types of blood vessels in the body: arteries, veins, and capillaries.
  • Arteries carry blood away from the heart. They have thick, muscular walls to withstand the high pressure of blood pumped by the heart.
  • Veins return blood to the heart. They have thinner walls and contain valves to prevent the backward flow of blood.
  • Capillaries are the smallest blood vessels where exchange of materials occurs. Their walls are one cell thick, allowing for easy diffusion of substances.

Blood

  • Blood is a connective tissue composed of plasma, red blood cells, white blood cells, and platelets.
  • Red blood cells contain haemoglobin, a protein responsible for oxygen transport. Their biconcave shape increases their surface area, allowing for better gas exchange.
  • White blood cells function in the immune response, they protect the body against pathogens by engulfing them or producing antibodies.
  • Platelets are involved in blood clotting which prevents excess blood loss when a blood vessel is damaged.

Cardiovascular Diseases

  • Cardiovascular diseases represent a significant health concern and include conditions like atherosclerosis and heart attacks.
  • A healthy lifestyle including regular exercise, a balanced diet, and avoiding smoking can reduce the risk of these diseases.

Double Circulation

  • Mammals exhibit double circulation, with the blood passing through the heart twice in a complete circuit – once for pulmonary circulation (lung circulation) and once for systemic circulation (body circulation). This ensures efficient separation of oxygenated and de-oxygenated blood, which allows for higher metabolic rates and activity levels.

Course material for Biology (Combined), module Transport, topic Transport in Mammals

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