iGCSE Biology (Triple) OxfordAQA

This subject is broken down into 30 topics in 6 modules:

  1. Organisation 5 topics
  2. Bioenergetics 6 topics
  3. Ecology 4 topics
  4. Organisms' Interaction with the Environment 8 topics
  5. Inheritance 5 topics
  6. Variation and Evolution 2 topics
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  • 30
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  • 11,424
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This page was last modified on 28 September 2024.

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Biology (Triple)

Organisation

Organisation: Cell Structure

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Organisation: Cell Structure

Basics of Cell Structure

  • All living organisms are made up of cells, which are often called the building blocks of life.
  • Cells vary greatly in terms of their shape and function, but all cells share common characteristics.
  • Cells can be categorised into two primary types: prokaryotes and eukaryotes.
  • Prokaryotic cells, such as bacteria, have no discernible nucleus and contain fewer organelles than eukaryotes.
  • Eukaryotic cells, found in plants, animals, fungi, and protists, have a well-defined nucleus and are more complex than prokaryotes.

Components of Eukaryotic Cells

  • Each eukaryotic cell has a nucleus that contains the genetic information (DNA) and is responsible for controlling cell activity.
  • Cytoplasm is the cellular material outside the nucleus in which the organelles are located.
  • Mitochondria are the powerhouses of the cell, generating energy for cell activities.
  • Ribosomes are where proteins are synthesised as per the instructions from DNA.
  • Cell membrane is a dynamic structure that controls the movement of substances in and out of the cell.

Plant Cell Structure

  • Plant cells contain all the eukaryotic components but have a few additional structures.
  • Chloroplasts are involved in photosynthesis, converting sunlight into glucose for energy.
  • The cell wall, made primarily of cellulose, provides structure and support to the plant.
  • A large vacuole, filled with cell sap, helps to maintain the cell’s shape.

Animal Cell Structure

  • Animal cells contain typical eukaryotic components but lack certain features found in plant cells, such as chloroplasts, cell walls, and large vacuoles.
  • Animal cells often contain small vacuoles which facilitate storage and transport processes within the cell.

Microscopy in Cell Study

  • Microscopy has been pivotal in the study of cell structure and function.
  • Light microscopy allows for the visualisation of cell structures like the cell membrane, nucleus and cytoplasm.
  • Electron microscopy offers a much higher resolution and can reveal much smaller structures such as ribosomes and the detailed structure of the cell membrane.

Specialisation in Cells

  • Cells often specialise to perform specific functions. This concept is referred to as cell differentiation.
  • Some examples of specialised cells include nerve cells, muscle cells, sperm cells, and root hair cells. They have unique structures that enable them to fulfil their specific roles.

Importance of Cell Organisation

  • From tissue formation to complex organisms, cells organise at various levels.
  • Cells of a similar type group together to form tissues, with a common function.
  • Multiple tissues come together to form organs, such as the heart or lungs.
  • Multiple organs work together to form organ systems, such as the digestive system or cardiovascular system.

Remember, revisiting each of the points and understanding how they work together will ensure a strong grasp of cell structure and organisation in your biology revision.

Course material for Biology (Triple), module Organisation, topic Organisation: Cell Structure

Biology (Triple)

Organisms' Interaction with the Environment

Environment: The Human Nervous System

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Environment: The Human Nervous System

The Basic Structure and Functions of the Human Nervous System

  • The nervous system is a complex network of nerves and cells, or neurones, that carry messages to and from the brain and spinal cord to various parts of the body.

  • The central nervous system (CNS) consists of the brain and spinal cord. It is responsible for processing information and controlling the majority of functions of the body and mind.

  • The peripheral nervous system (PNS) consists of all the nerves outside the CNS. It connects the CNS to the limbs and organs.

  • The PNS is further divided into the somatic nervous system, which controls voluntary muscle movements and the autonomic nervous system, which controls involuntary actions like breathing and digestion.

Components of the Nervous System

  • Neurones are the basic unit of the nervous system. They are specialised cells designed to transmit electrical signals or nerve impulses.

  • Each neurone is composed of a cell body, a dendrites - extensions that receive signals from other neurones, and an axon - a long nerve fibre that conducts the impulse away from the cell body.

  • Synapses are junctions where two neurones meet. They allow for the transmission of nerve impulses through the release of neurotransmitters.

Response to Stimuli

  • The sequence of events following a stimulus is known as a reflex arc. This includes the following stages: reception by sensory neurones, transmission to the CNS, transmission to the effector organs through motor neurones, and the response by effector organs.

  • Reflex actions are rapid, involuntary responses to stimuli. They are important for survival, as they can help to prevent injury by allowing quick reaction to potentially harmful situations.

  • Coordination occurs as a result of two systems in our body – the nervous system and the Endocrine system. The nervous system provides quick responses while the endocrine system generally provides slower, long term responses.

Key Parts of the Brain

  • The cerebrum is the largest part of the brain. It controls intelligence, creativity, emotion, and sensory processing.

  • The cerebellum is responsible for coordinating voluntary movements, maintaining posture and balance.

  • The medulla oblongata controls vital life-sustaining functions such as heartbeat, breathing, and digestion.

  • The hypothalamus regulates body temperature, hunger, thirst, and some aspects of behaviour.

In revising the human nervous system, make sure to understand these components, their functions and how they work together to react to changes in the environment. This coordination and response to changes is crucial for survival and overall well-being.

Course material for Biology (Triple), module Organisms' Interaction with the Environment, topic Environment: The Human Nervous System

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