BackGeneral Biology: Core Concepts and Ecological Principles
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Introduction to the Science of Life
Characteristics of Living Organisms
Biology is the scientific study of life, and all living organisms share several fundamental characteristics that distinguish them from non-living matter.
Reproduction: The ability to produce offspring, either sexually or asexually.
Growth and Development: Organisms grow and develop according to specific instructions coded in their genes.
Energy and Matter Use: All living things require energy and matter, often obtained through processes such as photosynthesis or cellular respiration. ATP and carbohydrates are key molecules.
Cells: The cell is the basic unit of life; organisms may be unicellular or multicellular.
Order: Living things exhibit complex but ordered structures.
Response to the Environment: Organisms sense and respond to environmental stimuli to maintain optimal conditions.
Evolution: Populations evolve over time, adapting to their environments.
Homeostasis is the process by which organisms maintain internal equilibrium, such as temperature regulation in elephants.
Viruses are not considered living because they lack cellular structure and cannot reproduce independently.
The Chemistry of Life
Atoms, Elements, and Molecules
All matter is composed of atoms, which combine to form molecules. Elements are substances that cannot be broken down by chemical reactions.
Atomic Number: Number of protons in an atom.
Atomic Weight: Sum of protons and neutrons.
Of the 92 natural elements, only 25 are used by living cells. Four elements (oxygen, carbon, hydrogen, nitrogen) make up the bulk of living cells.
Water and Its Properties
Water is a polar molecule, with unique properties such as cohesion, adhesion, and the ability to form hydrogen bonds. These properties are essential for life.
Cohesion: Water molecules stick to each other, creating surface tension.
Adhesion: Water molecules stick to other substances.
Ice Floating: Ice is less dense than liquid water, allowing it to float and insulate aquatic life.
Solutions, Acids, and Bases
Most life-supporting chemical reactions occur in water. The pH scale measures hydrogen ion concentration, ranging from 0 (acidic) to 14 (basic).
Acid: Releases H+ ions in solution.
Base: Decreases H+ ion concentration.
Buffer: Resists changes in pH.
Energy and Life
Energy Flow and Chemical Cycling
Energy flows through ecosystems, primarily from the sun, and is transferred between organisms via food webs and trophic levels. Chemical nutrients cycle through ecosystems, such as the carbon and nitrogen cycles.
Producers: Capture sunlight and convert it to chemical energy via photosynthesis.
Consumers: Obtain energy by eating other organisms.
Decomposers: Break down dead organisms, recycling nutrients.
Photosynthesis and Cellular Respiration
Photosynthesis converts solar energy into chemical energy (sugars), while cellular respiration releases energy from sugars to produce ATP.
Photosynthesis: Occurs in chloroplasts, uses CO2 and H2O to produce sugars and O2.
Cellular Respiration: Occurs in mitochondria, uses sugars and O2 to produce ATP, CO2, and H2O.
Ecology: Interactions and Population Dynamics
Levels of Ecological Organization
Ecology studies interactions between organisms and their environment, organized into levels: organism, population, community, ecosystem, and biosphere.
Population: Group of individuals of the same species in a given area.
Community: All populations of different species in an area.
Ecosystem: All biotic and abiotic components in an area.
Biosphere: All ecosystems on Earth.
Population Growth Models
Population growth can be described by two main models: exponential and logistic growth.
Exponential Growth: Rapid, unlimited growth in a population with abundant resources. Produces a J-shaped curve.
Logistic Growth: Growth slows as population approaches carrying capacity, producing an S-shaped curve.
Carrying Capacity: Maximum population size an environment can sustain.
Species Interactions
Species interact in various ways, affecting population dynamics and community structure.
Type of Interaction | Effect on Population 1 | Effect on Population 2 | Example |
|---|---|---|---|
Competition | Negative | Negative | Different species of plants compete for sunlight |
Mutualism | Positive | Positive | Flowers and pollinators benefit each other |
Predation | Positive | Negative | Cheetahs hunt gazelles |
Herbivory | Positive | Negative | Deer eat forest plants |
Parasitism/Pathogens | Positive | Negative | Heartworms in dogs |
Commensalism | Positive | Neutral | Egrets and cattle |
Trophic Structure and Food Webs
Trophic structure describes feeding relationships within a community. Food chains and food webs illustrate energy transfer and species interactions.
Trophic Levels: Producers, primary consumers, secondary consumers, tertiary consumers, apex predators, decomposers.
Food Web: Interconnected food chains showing complex relationships.
Trophic Cascades and Keystone Species
A trophic cascade occurs when changes at one trophic level affect multiple levels below. Keystone species have a disproportionate effect on ecosystem structure and diversity.
Global Climate Change and Human Impact
Greenhouse Effect and Climate Change
Greenhouse gases trap heat in Earth's atmosphere, maintaining habitable temperatures. Human activities have increased greenhouse gas concentrations, causing global warming and climate change.
Major Greenhouse Gases: CO2, CH4, N2O, H2O, O3, CFCs.
Greenhouse Effect: Sunlight warms Earth; greenhouse gases prevent heat from escaping.
Biogeochemical Cycles
Biogeochemical cycles describe the movement of elements through living and nonliving systems. The carbon and nitrogen cycles are essential for life.
Carbon Cycle: Involves photosynthesis, respiration, decomposition, and human activities.
Nitrogen Cycle: Involves nitrogen fixation, assimilation, nitrification, and denitrification.
Human Population Growth and Ecological Footprint
Human population growth has accelerated due to advances in health and technology, increasing the ecological footprint and impacting ecosystems.
Ecological Footprint: Area of land and water required to sustain one person.
Conservation Biology: Seeks to reverse biodiversity loss and sustain ecosystems.
Energy Conversion and Entropy
Energy Forms and Conservation
Energy can be converted from one form to another but cannot be created or destroyed (law of conservation of energy). Living organisms use chemical energy stored in molecules such as ATP.
Kinetic Energy: Energy of motion.
Potential Energy: Energy due to position or structure.
Chemical Energy: Stored in molecular bonds.
ATP: The Energy Currency of Cells
ATP (adenosine triphosphate) is the primary energy carrier in cells. Breaking a bond in ATP releases energy for cellular work.
ATP → ADP + Phosphate + Energy
Photosynthesis: Mechanism and Importance
Photosynthesis Process
Photosynthesis occurs in two stages: the light reactions and the Calvin cycle. Chlorophyll absorbs light energy, which is used to produce ATP and NADPH. The Calvin cycle uses these products to synthesize sugars from CO2.
Light Reactions: Capture energy from sunlight, produce ATP and NADPH.
Calvin Cycle: Uses ATP and NADPH to convert CO2 into sugars.
Chlorophyll is the primary pigment in chloroplasts, absorbing blue/violet and orange/red light, reflecting green/yellow.
Photosynthesis equation:
Biodiversity and Conservation
Biodiversity Levels and Benefits
Biodiversity includes genetic, species, and ecosystem diversity. It provides food, medicine, and ecosystem services.
Genetic Biodiversity: Variety of genes within a population.
Species Biodiversity: Number of species in an ecosystem.
Ecosystem Biodiversity: Variety of ecosystems on Earth.
Threats to biodiversity include overharvesting, invasive species, habitat destruction, pollution, and climate change.
Conservation biology aims to protect biodiversity and sustain ecosystems for future generations.
----------------------------------------
