Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms must maintain homeostasis to survive.

Subdisciplines of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Botany is the scientific study of plants.
• Cell biology studies the structure, function and behavior of cells.
• Ecology studies the interactions of living organisms with each other and their environment.
• Evolution is the study of the processes that have diversified life on Earth
• Genetics studies heredity and variation in organisms.
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa.
• Molecular biology studies the structure and function of biological macromolecules, including proteins and nucleic acids.
• Physiology studies the functions and mechanisms in a living system
• Zoology is the scientific study of animals.

Key Concepts in Biology

• Cell Theory: The cell is the basic unit of life, all living organisms are composed of one or more cells, and all cells arise from pre-existing cells.
• Gene Theory: Genes are the basic units of heredity and are composed of DNA. Genes provide the instructions for the structure and function of cells.
• Evolution: Life on Earth has evolved over time through the process of natural selection. New species arise, and existing species go extinct.
• Homeostasis: Living organisms maintain a stable internal environment despite changes in the external environment.
• Energy: All living organisms require energy to carry out life processes. Energy flows through ecosystems from producers to consumers.

The Cell

• The cell is the basic structural and functional unit of all known living organisms.
• It is the smallest unit of an organism that is considered living.
• Cells can be classified into two main types: prokaryotic and eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles. Bacteria and archaea are prokaryotes.
• Eukaryotic cells have a nucleus and other membrane-bound organelles, such as mitochondria and endoplasmic reticulum. Plants, animals, fungi, and protists are eukaryotes.
• Key cellular structures include the plasma membrane, cytoplasm, nucleus (in eukaryotes), ribosomes, and organelles.

Genetics

• Genetics is the study of heredity, the process by which traits are passed from parents to offspring.
• Genes are the basic units of heredity and are composed of DNA.
• DNA is a double-stranded molecule that carries the genetic instructions for the development, function, growth and reproduction of all known organisms.
• The sequence of DNA determines the traits of an organism.
• Genes are located on chromosomes, which are structures found in the nucleus of eukaryotic cells.
• During sexual reproduction, genes are passed from parents to offspring through gametes (sperm and egg cells).
• Mutations are changes in the DNA sequence that can lead to variation in traits.

Evolution

• Evolution is the process by which populations of organisms change over time.
• Natural selection is the driving force of evolution. Organisms with traits that are better suited to their environment are more likely to survive and reproduce, passing on those traits to their offspring.
• Over time, natural selection can lead to the adaptation of populations to their environment.
• New species can arise through the process of speciation.
• Evidence for evolution comes from a variety of sources, including the fossil record, comparative anatomy, and molecular biology.

Ecology

• Ecology is the study of the interactions of living organisms with each other and their environment.
• Ecosystems are communities of living organisms interacting with their physical environment.
• Energy flows through ecosystems from producers (plants) to consumers (animals).
• Nutrients cycle through ecosystems.
• Populations of organisms are regulated by factors such as competition, predation, and disease.
• Human activities can have a significant impact on ecosystems.

Classification of Living Things

• Taxonomy is the science of classifying and naming organisms.
• The current classification system uses a hierarchical system with eight levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• The three domains of life are: Bacteria, Archaea, and Eukarya.
• Bacteria and Archaea are prokaryotic organisms.
• Eukarya includes plants, animals, fungi, and protists.
• Scientific names are binomial, consisting of the genus and species names.
• The system helps scientists organize and understand the diversity of life on Earth.

Viruses

• Viruses are acellular infectious agents that can only replicate inside the living cells of other organisms.
• They consist of genetic material (DNA or RNA) surrounded by a protein coat called a capsid.
• Some viruses have an envelope, which is a membrane derived from the host cell.
• Viruses infect a wide variety of organisms, including bacteria, plants, and animals.
• Viral infections can cause a variety of diseases.
• Viruses are not considered living organisms because they cannot reproduce on their own.

Plants

• Plants are multicellular, eukaryotic organisms that belong to the kingdom Plantae.
• They are characterized by their ability to perform photosynthesis, which is the process of converting light energy into chemical energy.
• Plants have cell walls made of cellulose.
• Plants have a variety of adaptations that allow them to survive in different environments.
• Plants play a vital role in ecosystems by producing oxygen and providing food and shelter for other organisms.

Animals

• Animals are multicellular, eukaryotic organisms that belong to the kingdom Animalia.
• They are heterotrophic, meaning that they obtain their nutrition by consuming other organisms.
• Animals lack cell walls.
• Animals exhibit a wide variety of body plans and lifestyles.
• Animals play a vital role in ecosystems as consumers and decomposers.

Fungi

• Fungi are eukaryotic organisms that belong to the kingdom Fungi.
• They are heterotrophic, and obtain nutrients by absorption.
• Fungi have cell walls made of chitin.
• Fungi can be unicellular or multicellular.
• Fungi play a vital role in ecosystems as decomposers and symbionts.

The Human Body

• The human body is a complex organism composed of trillions of cells organized into tissues, organs, and organ systems.
• The major organ systems include the skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, and reproductive systems.
• The skeletal system provides support and protection for the body.
• The muscular system allows for movement.
• The nervous system controls and coordinates bodily functions.
• The endocrine system produces hormones that regulate bodily functions.
• The cardiovascular system transports blood throughout the body.
• The respiratory system allows for gas exchange.
• The digestive system breaks down food and absorbs nutrients.
• The urinary system removes waste products from the blood.
• The reproductive system allows for reproduction.