General Biology: Foundations, Evolution, and Ecology Study Notes

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How Science is Done

Scientific Method and Key Concepts

The scientific method is a systematic approach used to investigate natural phenomena, develop new knowledge, or correct and integrate previous knowledge. It relies on observation, hypothesis formation, experimentation, and analysis.

Assumption: A statement accepted as true without proof, serving as a starting point for further reasoning.
Observation: The act of noting and recording an event, characteristic, or behavior using the senses or instruments.
Hypothesis: A testable, falsifiable statement or prediction about the natural world.
Scientific Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence and repeatedly tested and confirmed through observation and experimentation.

Difference between Observation and Hypothesis: An observation is a direct record of a phenomenon, while a hypothesis is a proposed explanation for an observation.
Difference between Hypothesis and Scientific Theory: A hypothesis is a tentative explanation that can be tested, whereas a scientific theory is a comprehensive explanation supported by a large body of evidence.

Evolution

Key Terms and Concepts

Evolution is the process by which populations of organisms change over generations through variations in genetic material and environmental pressures.

Evolution: Change in the heritable characteristics of biological populations over successive generations.
Population: A group of individuals of the same species living in a specific area.
Genetic Change: Alterations in the genetic makeup of a population, often through mutation, gene flow, or genetic drift.
Mutation: A change in the DNA sequence, which can introduce new genetic variation.
Gene Flow: The transfer of genetic material between populations.
Genetic Drift: Random changes in allele frequencies in a population, especially in small populations.
Natural Selection: The process by which individuals with advantageous traits survive and reproduce more successfully.
Artificial Selection: The intentional breeding of organisms by humans for specific traits.
Speciation: The formation of new and distinct species in the course of evolution.
Allopatric Speciation: Speciation that occurs when biological populations are physically isolated by an extrinsic barrier and evolve intrinsic reproductive isolation.
Homologous Structures: Anatomical features that are similar in different species due to shared ancestry.
Analogous Structures: Features that serve similar functions in different species but do not share a common ancestral origin.

Mechanisms of Evolution

Mutation: Introduces new genetic variation into a population.
Gene Flow: Movement of genes between populations increases genetic diversity.
Genetic Drift: Causes random changes in allele frequencies, especially in small populations.
Natural Selection: Favors individuals with traits that increase survival and reproductive success.
Artificial Selection: Human-driven selection for desired traits.

Evidence for Evolution

Fossil Record: Provides evidence of past life forms and evolutionary transitions. Fossils are often incomplete, but patterns in the fossil record support evolutionary theory.
Biogeography: The geographic distribution of species supports evolution; similar species are often found in the same regions.
Comparative Anatomy and Developmental Biology: Homologous structures and embryonic similarities indicate common ancestry.
DNA Sequence Analysis: Genetic similarities among species reflect evolutionary relationships.
Experiments: Laboratory and field experiments demonstrate evolutionary processes in action.

Phylogenetics and Speciation

Phylogenetic Trees: Diagrams that represent evolutionary relationships among organisms. Changing the layout of branches can clarify relationships.
Reading Phylogenetic Trees: To determine which of two groups is more closely related, find their most recent common ancestor on the tree. The group sharing a more recent ancestor is more closely related.
Speciation: The process by which new species arise. Allopatric speciation occurs when populations are geographically isolated.

Ecology

Key Terms and Concepts

Ecology is the study of interactions among organisms and their environment, including the distribution and abundance of organisms, and the flow of energy and matter through ecosystems.

Population: A group of individuals of the same species in a given area.
Carrying Capacity: The maximum population size that an environment can sustain indefinitely.
Exponential Growth: Population growth under ideal conditions, with resources unlimited, resulting in a J-shaped curve.
Community: All the populations of different species living and interacting in an area.
Community Interactions: Includes competition, predation, mutualism, and other relationships.
Producer: An organism that can make its own food, usually through photosynthesis (e.g., plants).
Consumer: An organism that obtains energy by feeding on other organisms.
Autotroph: An organism that produces its own food from inorganic substances.
Heterotroph: An organism that obtains food by consuming other organisms.
Trophic Level: The position an organism occupies in a food chain.
Trophic Pyramid: A graphical representation showing the distribution of biomass or energy among trophic levels.
Principle of Competitive Exclusion: No two species can occupy the same niche in the same environment for a long time.

Population Growth and Carrying Capacity

Exponential Growth: Occurs when resources are unlimited. Population increases rapidly.
Carrying Capacity (K): The largest population that an environment can support. When population size approaches carrying capacity, growth slows and stabilizes.
Effect of Carrying Capacity: Limits population size; populations cannot grow indefinitely.

Studying Populations

Studying Individuals vs. Populations: Studying a single individual does not provide information about population-level characteristics such as genetic diversity, population size, or structure.
Population Data: Includes birth rates, death rates, immigration, emigration, and age structure.

Photosynthesis and Energy Flow

Photosynthesis: The process by which producers (e.g., plants) convert light energy into chemical energy (glucose).
Equation for Photosynthesis:

Energy Transfer: Only about 10% of the energy at one trophic level is transferred to the next; the rest is lost as heat.

Community Interactions and Fitness

Types of Interactions: Competition, predation, mutualism, commensalism, parasitism.
Effects on Fitness: Interactions can increase or decrease the reproductive success (fitness) of individuals involved.

Summary Table: Types of Community Interactions

Interaction Type	Effect on Species 1	Effect on Species 2	Example
Competition	Negative	Negative	Two plants competing for sunlight
Predation	Positive	Negative	Lion eating a zebra
Mutualism	Positive	Positive	Bees pollinating flowers
Commensalism	Positive	Neutral	Barnacles on a whale
Parasitism	Positive	Negative	Tapeworm in a mammal