Biology Overview and Cell Structure

Definition: Biology is the scientific study of life and living organisms.
Branches:
- Botany: Study of plants.
- Zoology: Study of animals.
- Microbiology: Study of microorganisms.
- Ecology: Study of interactions between organisms and their environment.
- Genetics: Study of heredity and variation in organisms.

Cell Theory:
- All living organisms are made of cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells:
- Prokaryotic: No nucleus, smaller, e.g., bacteria.
- Eukaryotic: Contains a nucleus, larger, e.g., plants and animals.

DNA Structure:
- Double helix; composed of nucleotides (adenine, thymine, cytosine, guanine).
Genes: Units of heredity; segments of DNA that encode proteins.
Mendelian Genetics:
- Law of Segregation: Alleles segregate during gamete formation.
- Law of Independent Assortment: Genes for different traits can segregate independently.

Theory of Evolution:
- Proposed by Charles Darwin; species evolve over time through natural selection.
Natural Selection:
- Organisms with favorable traits are more likely to survive and reproduce.

Ecosystem Components:
- Biotic: Living things (plants, animals, microorganisms).
- Abiotic: Non-living things (water, soil, climate).
Food Chains and Webs:
- Producers (plants) → Primary consumers (herbivores) → Secondary consumers (carnivores) → Tertiary consumers.

Organ Systems in Animals:
- Circulatory: Transports blood and nutrients.
- Respiratory: Exchanges gases (O2 and CO2).
- Digestive: Breaks down food and absorbs nutrients.
- Nervous: Controls bodily functions through signals.

Photosynthesis:
- Process by which plants convert light energy into chemical energy (glucose).
- Occurs in chloroplasts; involves chlorophyll.
Plant Structure:
- Roots: Absorb water and nutrients.
- Stems: Support and transport.
- Leaves: Main site for photosynthesis.

Types of Microorganisms:
- Bacteria: Single-celled, can be beneficial or harmful.
- Viruses: Infectious agents that require a host to reproduce.
- Fungi: Decomposers; can be single-celled (yeasts) or multicellular (molds).

Protein Synthesis:
- Transcription: DNA is transcribed to mRNA.
- Translation: mRNA is translated into amino acids to form proteins.
Enzymes: Biological catalysts that speed up chemical reactions in cells.

Macromolecules:
- Carbohydrates: Provide energy (sugars, starches).
- Proteins: Made of amino acids; perform various functions (enzymes, structural).
- Lipids: Fats and oils; energy storage, cell membranes.
- Nucleic Acids: DNA and RNA; store and transmit genetic information.

Speciation: Formation of new species due to evolutionary processes.
Adaptive Radiation: Diversification of a group of organisms into forms filling different ecological niches.

Homeostasis: The ability of an organism to maintain stable internal conditions.
Biological Classification: Organisms are classified into hierarchical categories (domain, kingdom, phylum, class, order, family, genus, species).
Symbiosis: Interaction between different organisms, which can be mutualistic, commensalistic, or parasitic.

Biology is the study of life and living organisms, encompassing various fields and interactions.
Branches of biology include:
- Botany: Focuses on plant life and processes.
- Zoology: Studies animal behavior, structure, and classification.
- Microbiology: Examines microorganisms and their roles in ecosystems.
- Ecology: Looks at interactions between organisms and their environment.
- Genetics: Investigates heredity, genes, and variation within species.

Cell Theory outlines three fundamental principles:
- All living beings are composed of cells.
- The cell serves as the basic structural and functional unit of life.
- New cells originate from existing cells through division.
Types of cells:
- Prokaryotic Cells: Lack a nucleus, typically smaller (e.g., bacteria).
- Eukaryotic Cells: Have a defined nucleus, generally larger (e.g., plant and animal cells).

DNA is structured as a double helix, made up of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G).
Genes are segments of DNA that function as units of heredity and encode specific proteins.
Mendelian Genetics includes:
- Law of Segregation: Alleles separate during gamete formation.
- Law of Independent Assortment: Genes for different traits segregate independently in gametes.

The Theory of Evolution, primarily proposed by Charles Darwin, articulates that species adapt and change over time through a process called natural selection.
Natural Selection highlights survival and reproductive advantages granted to organisms with favorable traits.

Ecosystems consist of:
- Biotic Components: Living entities such as plants, animals, and microorganisms.
- Abiotic Components: Non-living elements like water, soil, and climate.
Food Chains and Food Webs describe energy transfer:
- Producers (plants) → Primary consumers (herbivores) → Secondary consumers (carnivores) → Tertiary consumers.

Major organ systems in animals include:
- Circulatory System: Transports oxygen, nutrients, and waste.
- Respiratory System: Facilitates gas exchange (oxygen in, carbon dioxide out).
- Digestive System: Breaks down food and absorbs essential nutrients.
- Nervous System: Coordinates body activities through electrical signals.

Photosynthesis is the process where plants convert sunlight into glucose, occurring in chloroplasts with chlorophyll as the key pigment.
Basic structures of plants:
- Roots: Absorb water and nutrients from the soil.
- Stems: Provide support and transport materials.
- Leaves: Primary site for photosynthesis.

Various types of microorganisms include:
- Bacteria: Unicellular organisms that can play beneficial or harmful roles.
- Viruses: Require a host to reproduce and can cause diseases.
- Fungi: Decomposers that can exist as single-celled (yeasts) or multicellular (molds).

Protein Synthesis involves two main processes:
- Transcription: Conversion of DNA into messenger RNA (mRNA).
- Translation: mRNA is used to assemble amino acids into proteins.
Enzymes are proteins that act as biological catalysts, accelerating chemical reactions in cells.

Four main macromolecules are crucial for life:
- Carbohydrates: Source of energy including sugars and starches.
- Proteins: Comprised of amino acids, essential for various cellular functions and structures.
- Lipids: Fats and oils, important for energy storage and cell membrane structure.
- Nucleic Acids: DNA and RNA, responsible for genetic information storage and transmission.

Speciation is the process through which new species arise through mechanisms of evolution.
Adaptive Radiation describes how a lineage diversifies into multiple forms that exploit different ecological niches.

Homeostasis: The ability of organisms to maintain stable internal environments despite external changes.
Biological Classification organizes living organisms into hierarchical groups: domain, kingdom, phylum, class, order, family, genus, species.
Symbiosis refers to interactions among different organisms, including mutualism (benefits both), commensalism (one benefits, the other unaffected), and parasitism (one benefits at the expense of the other).