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Study Notes

Biology - First Grade Study Notes

What is biology?
- Biology is the natural science that examines life and living beings, encompassing their physical structure, chemical processes, molecular interactions, physiological functions, and evolution.
- It recognizes the cell as the fundamental unit of life, genes as the basic units of heredity, and evolution as the driving force behind the creation and extinction of species.
Why study biology?
- Biology is crucial for understanding human bodies, natural resources, and environmental threats.
- It's essential for medical advancements, allowing doctors to combat diseases by comprehending disease-causing pathogens.
- It's vital for understanding and treating hereditary diseases like hemophilia and Down syndrome.
Subdivisions of biology:
- Cellular biology (cytology)
- Molecular biology
- Physiology
- Genetics
- Microbiology
- Zoology
- Botany
- Clinical biology
- Development biology
- Marine biology
- Ecology
Cell:
- The cell is the fundamental structural, functional, and biological unit of all known organisms.
- It's comprised of various components, known as organelles, which are suspended within the cytoplasm, a gelatinous matrix enclosed by the cell membrane.
- All cells possess a cell membrane, a nucleus (containing DNA), and mitochondria (energy-generating structures).
- Some cells, such as red blood cells, lack certain organelles.
Types of cells:
- Prokaryotic cells: Single-celled organisms without a membrane-enclosed nucleus or other organelles. Examples: bacteria and archaea.
- Eukaryotic cells: Single-celled or multi-celled organisms possessing a membrane-bound nucleus and other organelles. Examples: plants, animals, fungi, protozoa, and algae.
Plant cells:
- Plant cells are enclosed by a rigid cell wall, unlike animal cells.
- They often contain large vacuoles that can account for up to 75% of the cell volume.
- Many contain a chloroplast, enabling photosynthesis.
Animal cells:
- Animal cells lack a cell wall, making their structure flexible.
- Animal cells vary according to their functions and contain various organelles.
- Animal bodies are made from four main tissue types: epithelial, connective, nervous, and muscle tissues.
Function of human cells:
- Cells in the human body have diverse functions based on type and location.
- Within cells, organelles work synergistically for essential functions such as nutrient intake, substance processing, creation of new substances, cell reproduction, and energy production.
- Specialized cells like those in the human sperm have projections enabling movement.