Introduction to Biology

• Biology is the scientific study of life and living organisms.
• It explores the structure, function, growth, origin, evolution, and distribution of living things.
• 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 share key characteristics including being composed of cells, using metabolism, being able to reproduce, being able to maintain homeostasis, being able to pass on traits to offspring, and grow/develop.

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Botany studies plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell biology studies the structure and function of cells, the basic units of life.
• Ecology studies the interactions of organisms with each other and their environment.
• Evolutionary biology studies the evolutionary processes that have produced the diversity of life on Earth.
• Genetics studies genes, heredity, and variation in living organisms.
• Microbiology studies microorganisms, including bacteria, viruses, fungi, and protozoa.
• Molecular biology studies the molecular basis of biological activity between biomolecules in cells.
• Physiology studies the functions and mechanisms of living organisms and their parts.
• Zoology studies animals, including their physiology, anatomy, behavior, ecology, evolution, and classification.

Characteristics of Life

• Organization: Living things exhibit a high level of organization, from cells to tissues, organs, and systems.
• Metabolism: Living organisms carry out chemical reactions to obtain and use energy.
• Anabolism: Building up complex molecules from simpler ones.
• Catabolism: Breaking down complex molecules into simpler ones.
• Homeostasis: Maintaining a stable internal environment despite external changes.
• Growth: Increase in size or cell number.
• Reproduction: Producing offspring, either sexually or asexually.
• Response to stimuli: Reacting to changes in the environment.
• Evolution: Change in the genetic makeup of a population over time.
• Adaptation: Inherited trait that enhances survival and reproduction in a specific environment.

Cell Theory

• All living organisms are composed of one or more cells.
• The cell is the basic unit of structure and function in organisms.
• All cells arise from pre-existing cells.

Levels of Biological Organization

• Molecular: Atoms combine to form molecules like DNA, RNA, and proteins.
• Cellular: Molecules organize into cells, the basic unit of life.
• Tissue: Similar cells performing a specific function are organized into tissues.
• Organ: Different tissues combine to form organs, such as the heart, lungs, and brain.
• System: Organs work together to perform a specific function, forming organ systems like the digestive system and circulatory system.
• Organism: All organ systems function together to form a complete living organism.
• Population: A group of individuals of the same species living in the same area.
• Community: All the different populations of species living in the same area.
• Ecosystem: The community of organisms and their physical environment, interacting as a functional unit.
• Biosphere: All the ecosystems on Earth, encompassing all living organisms and their environments.

Scientific Method

• Observation: Observing a phenomenon or identifying a problem.
• Hypothesis: Formulating a testable explanation for the observation.
• Prediction: Making a specific, testable statement based on the hypothesis.
• Experimentation: Designing and conducting experiments to test the prediction.
• Analysis: Analyzing the data collected during the experiment.
• Conclusion: Drawing conclusions based on the analysis and determining whether the hypothesis is supported or refuted.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Evolutionary processes give rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules.
• Natural selection is a key mechanism of evolution, where organisms with traits better suited to their environment are more likely to survive and reproduce.
• Genetic variation within a population is essential for evolution, providing the raw material for natural selection.
• Adaptation: A trait with a functional role in the life of an organism that is maintained and evolved by means of natural selection.

Genetics

• Genes are the units of heredity, carrying information from one generation to the next.
• DNA (deoxyribonucleic acid) is the molecule that carries genetic information in most organisms.
• RNA (ribonucleic acid) plays various roles in gene expression, including transcription and translation.
• Mutation is a change in the DNA sequence, which can lead to variation in traits.
• Inheritance patterns: The rules governing the transmission of traits from parents to offspring.

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Populations: Groups of individuals of the same species living in the same area.
• Communities: Assemblages of different populations of species living in the same area.
• Ecosystems: Communities of organisms and their physical environment, interacting as a functional unit.
• Biomes: Large-scale ecosystems characterized by specific climate conditions and dominant plant communities.
• Biodiversity: The variety of life in a particular habitat or ecosystem.

Classification of Living Things

• Taxonomy: The science of classifying and naming organisms.
• The Linnaean system of classification uses a hierarchical system:
• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

The Three Domains of Life

• Bacteria: Prokaryotic microorganisms with diverse metabolic capabilities.
• Archaea: Prokaryotic microorganisms that often inhabit extreme environments.
• Eukarya: Organisms with cells containing a nucleus and other membrane-bound organelles.
• Includes protists, fungi, plants, and animals.

Viruses

• Acellular infectious agents that require a host cell to replicate.
• Consist of genetic material (DNA or RNA) surrounded by a protein coat.
• Can infect a wide range of organisms, causing various diseases.