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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Tissue Organisation
In biology, organisation is all about how living things are structured. Imagine building a house - you need bricks, wood, glass and other materials. Similarly, living organisms are built from different components arranged in levels of increasing complexity. Tissues are a crucial level in this organisation.
Key Definitions:
Living organisms are organised in a hierarchy of increasing complexity:
Cells → Tissues → Organs → Organ Systems → Organism
Each level builds upon the previous one, creating more complex structures with specialised functions.
Animals have four main types of tissues, each with specific functions and characteristics. These tissues work together to form the various organs in an animal's body.
Epithelial tissue covers body surfaces and lines cavities. These cells are tightly packed with little space between them.
Functions:
Example: The skin's outer layer is made of epithelial tissue that protects your body from germs, chemicals and dehydration.
Muscular tissue is made up of cells that can contract and relax, allowing movement.
Types:
Example: When you pick up a pencil, your skeletal muscles contract to move your arm and fingers.
Nervous tissue is specialised to carry electrical signals throughout the body.
Components:
Example: When you touch something hot, neurons in your fingers send signals to your brain, which then sends signals to your muscles to pull away.
Connective tissue supports, connects and separates different types of tissues and organs in the body.
Types:
Example: The bones in your skeleton provide support and protection for your organs.
Plants also have specialised tissues, but they're different from animal tissues because plants have different needs. Plant tissues can be grouped into three main systems.
Forms the outer protective covering of the plant.
Includes:
Makes up most of the plant's body and performs various functions.
Includes:
Transports water, minerals and food throughout the plant.
Includes:
Different tissues work together to form organs with specific functions. Each organ contains multiple tissue types arranged in a way that allows the organ to perform its job effectively.
The heart pumps blood throughout the body and contains:
A plant leaf is an organ specialised for photosynthesis and contains:
Organs work together in organ systems to perform complex functions necessary for survival. Each system has a specific role in maintaining homeostasis (balance) in the body.
The digestive system is a perfect example of how different organs with various tissues work together. When you eat a sandwich:
Each organ contains multiple tissue types working together and all organs work as a system to digest food and absorb nutrients.
Tissues are specialised to perform specific functions. This specialisation allows organisms to be more efficient and adapt to their environments.
Let's look at some fascinating examples of how tissues are specialised for specific functions:
The retina at the back of your eye contains specialised nervous tissue with photoreceptor cells called rods and cones. Rods detect light in dim conditions, while cones detect colour in bright light. This specialisation allows us to see in different lighting conditions.
Cacti have specialised dermal and ground tissues that help them survive in desert environments. Their epidermis has a thick waxy cuticle to prevent water loss and they have modified leaves (spines) to reduce surface area. Their stem tissue can expand to store water during rare rainfall events.
Tissue organisation is crucial for the proper functioning of living organisms. When tissues don't develop or function correctly, it can lead to diseases and disorders.
Understanding tissue organisation helps medical professionals diagnose and treat diseases:
Tissue organisation is a fundamental concept in biology that helps us understand how living organisms function. From the microscopic level of cells to the complex interactions of organ systems, the organisation of tissues allows for specialisation and efficiency.
Remember these key points:
Understanding tissue organisation helps us appreciate the complexity and elegance of living organisms and provides the foundation for medical advances that improve human health.
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