Introduction to Biology

• Biology is the scientific study of life.
• It encompasses the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms.

Characteristics of Life

• Living things share key characteristics: order, sensitivity or response to the environment, reproduction, adaptation, growth and development, regulation/homeostasis, energy processing, and evolution.
• Order: Living things exhibit complex organization, from atoms to molecules to organelles to cells to tissues to organs to organ systems to organisms.
• Sensitivity: Organisms respond to stimuli, such as light, temperature, touch, or chemical signals.
• Reproduction: Organisms reproduce to pass on their genetic information.
• Adaptation: Organisms evolve adaptations that enhance their survival and reproduction in specific environments.
• Growth and Development: Organisms grow and develop according to instructions coded for by their genes.
• Regulation/Homeostasis: Regulatory mechanisms maintain a stable internal environment despite external fluctuations.
• Energy Processing: Organisms obtain and utilize energy to power life processes.
• Evolution: Over time, populations of organisms evolve, leading to diversity and adaptation.

Hierarchical Organization of Life

• Life is organized on several structural levels.
• These levels include: molecules, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
• Molecules: Atoms combine to form molecules such as DNA and proteins.
• Cells: Molecules form cells, the basic unit of life.
• Tissues: Similar cells form tissues (e.g., muscle tissue).
• Organs: Tissues make up organs (e.g., the heart).
• Organ Systems: Organs that work together form organ systems (e.g., the circulatory system).
• Organisms: Organ systems make up organisms (e.g., a human).
• Populations: Groups of the same organism in the same place form populations.
• Communities: Different populations of organisms form communities.
• Ecosystems: Communities interact with their physical environment to form ecosystems.
• Biosphere: All of the ecosystems on Earth make up the biosphere.

Emergent Properties

• Emergent properties are novel properties that arise at each step of biological organization.
• They are due to the arrangement and interactions of parts as complexity increases.
• Example: Photosynthesis occurs in an intact chloroplast but will not occur if the chloroplast components are simply mixed in a test tube. The specific organization is essential.

The Cell

• The cell is the basic unit of life.
• All organisms are made of cells.
• Cells are enclosed by a membrane.
• They contain DNA and other molecules.
• There are two main types of cells: prokaryotic and eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles; include bacteria and archaea.
• Eukaryotic cells have a nucleus and other membrane-bound organelles; include protists, fungi, plants, and animals.

Genes and Inheritance

• Genes are the units of heredity.
• They are made of DNA (deoxyribonucleic acid).
• DNA controls the structure and function of cells.
• DNA is inherited from parents to offspring.
• Genes encode the information necessary to build proteins.
• The flow of genetic information: DNA -> RNA -> Protein.
• DNA is transcribed into RNA.
• RNA is translated into protein.

Evolution

• Evolution is the process of change that has transformed life on Earth.
• It explains the unity and diversity of life.
• Charles Darwin proposed the theory of natural selection as a mechanism for evolution.
• Natural selection: Individuals with traits that are better suited to their environment are more likely to survive and reproduce.
• The result is adaptation.

Taxonomy

• Taxonomy is the branch of biology that names and classifies species.
• Organisms are classified into a hierarchy of groups.
• The major levels of classification: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• The three domains of life are: Bacteria, Archaea, and Eukarya.
• Bacteria and Archaea are prokaryotic.
• Eukarya includes eukaryotic organisms.

Scientific Inquiry

• Biology is a science.
• Science uses observation and experimentation to understand the world.
• Scientific Method:
• Observation: Observing a phenomenon or asking a question.
• Hypothesis: Formulating a testable explanation for the observation.
• Experiment: Designing and conducting experiments to test the hypothesis.
• Data Analysis: Analyzing the results of the experiments.
• Conclusion: Drawing conclusions based on the data and determining whether the hypothesis is supported or not.
• A scientific theory is a well-substantiated explanation of some aspect of the natural world.
• It is based on a body of facts that have been repeatedly confirmed through observation and experiment.

Energy Flow and Chemical Cycling

• Life requires energy.
• Energy flows through ecosystems.
• It typically enters as light and exits as heat.
• Chemical elements cycle within ecosystems.
• Producers (e.g., plants) convert sunlight into chemical energy through photosynthesis.
• Consumers (e.g., animals) obtain energy by feeding on producers or other consumers.
• Decomposers break down dead organisms and waste products, recycling chemical elements back into the environment.

Interactions in Ecosystems

• Organisms interact with each other and with their environment.
• Interactions can be beneficial, harmful, or neutral.
• Examples: competition, predation, mutualism, parasitism, commensalism.
• Populations are affected by interactions with other organisms and by the availability of resources.

Homeostasis

• Homeostasis is the ability of an organism to maintain a stable internal environment.
• It is essential for survival.
• Homeostatic mechanisms regulate temperature, pH, water balance, and other internal conditions.
• Feedback mechanisms play a crucial role in maintaining homeostasis.

Life Processes

• Life processes include a variety of functions essential for sustaining life.
• Nutrition: Obtaining and processing nutrients for energy and growth.
• Respiration: The process of releasing energy from food.
• Transport: Movement of substances within the organism.
• Excretion: Removal of waste products.
• Reproduction: Production of new individuals.
• Growth: Increase in size and complexity.
• Regulation: Control and coordination of bodily functions.

Nutrition

• Autotrophs: Organisms that produce their own food (e.g., plants through photosynthesis).
• Heterotrophs: Organisms that obtain food from other organisms (e.g., animals).
• Nutrients: Substances that provide nourishment essential for growth and the maintenance of life.
• Macronutrients: Needed in large quantities (e.g., carbohydrates, proteins, fats).
• Micronutrients: Needed in small quantities (e.g., vitamins, minerals).

Respiration

• Aerobic respiration: Requires oxygen to break down glucose and produce energy (ATP).
• Anaerobic respiration: Does not require oxygen (e.g., fermentation).
• ATP (adenosine triphosphate): The main energy currency of cells.

Transport

• In unicellular organisms, transport occurs through the cell membrane.
• In multicellular organisms, specialized transport systems are present (e.g., circulatory system in animals, vascular system in plants).
• Diffusion and osmosis are important transport mechanisms.

Excretion

• The process of removing metabolic waste products from the body.
• Organs involved in excretion: kidneys (urine), lungs (carbon dioxide), skin (sweat).

Reproduction

• Asexual reproduction: Involves one parent and produces genetically identical offspring (e.g., binary fission, budding).
• Sexual reproduction: Involves two parents and produces genetically diverse offspring.
• Meiosis: Cell division that produces gametes (sperm and egg cells).
• Fertilization: Fusion of gametes to form a zygote.

Growth

• Increase in size and cell number.
• Cell division (mitosis) is essential for growth and repair.
• Development: The process of change from a zygote to a mature organism.

Regulation

• Maintaining stable internal conditions (homeostasis).
• Nervous system: Rapid communication and coordination using electrical and chemical signals.
• Endocrine system: Slower, longer-lasting communication using hormones.
• Feedback mechanisms: Control systems that regulate physiological processes.
• Negative feedback: Reduces the original stimulus (e.g., regulation of body temperature).
• Positive feedback: Enhances the original stimulus (e.g., blood clotting).