General Biology Exam 1 Study Guide: Cancer, Evolution, Ecology, and Ecosystems

Chapter 18 – Section 18.5 Only: Cancer

Uncontrolled Cell Division and Cancer

Cancer is characterized by the uncontrolled division of cells, often due to mutations in genes that regulate the cell cycle. While the risk of mutations can be inherited, most cancers are not usually inherited directly.

• Cell Cycle Regulation: Normal cell division is tightly controlled by regulatory proteins. Mutations in these proteins can lead to unchecked cell growth.

• Geographic Variation: The incidence of different cancers varies by region, suggesting environmental and lifestyle factors play a role in causing mutations.

Genetic Mutations and Cancer

• Proto-oncogenes: Genes that normally stimulate cell division. When mutated, they can become oncogenes (like a stuck accelerator), causing excessive cell division and acting as dominant mutations.

• Tumor Suppressor Genes: Genes that inhibit cell division (the brakes). When both alleles are mutated or lost, the cell loses control over division. These are typically recessive mutations.

• p53 Gene: A key tumor suppressor gene. Mutations in p53 are present in about 50% of all human cancers.

Colorectal Cancer and Inherited Predisposition

• Multiple gene mutations contribute to the progression of colorectal cancer.

• Inherited predisposition means a person may inherit one or more mutations, increasing their risk, but additional mutations are usually required for cancer to develop.

Example: Familial adenomatous polyposis is an inherited condition that increases colorectal cancer risk due to inherited mutations in tumor suppressor genes.

Chapter 1 – Evolution, Themes of Biology, and Scientific Inquiry

General Themes of Biology

• Prokaryotes vs. Eukaryotes: Prokaryotes (Bacteria and Archaea) lack a nucleus, while eukaryotes (plants, animals, fungi, protists) have a nucleus and membrane-bound organelles.

• Cell Membranes: The basic structure is a phospholipid bilayer with embedded proteins, providing selective permeability.

Unity and Diversity of Life

• Unity: All life shares a common ancestor, reflected in shared genetic code and cellular structures.

• Diversity: Differences arise due to accumulation of genetic changes after species diverge.

• Domains of Life: Three domains: Bacteria, Archaea, and Eukarya (which includes Kingdoms Animalia, Plantae, Fungi, and Protists).

Natural Selection

• Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring.

• Key Points: Variation, inheritance, differential survival and reproduction.

Chapter 53 – Population Ecology

Population Structure and Growth

• Population: A group of individuals of the same species living in a specific area.

• Density: Number of individuals per unit area or volume.

• Dispersion: The pattern of spacing among individuals (clumped, uniform, random).

Survivorship Curves

• Type I: High survival in early/middle life, drops in old age (e.g., humans).

• Type II: Constant death rate (e.g., some birds).

• Type III: High death rate early, survivors live long (e.g., oysters).

Exponential vs. Logistic Growth

• Exponential Growth: Population increases under ideal conditions, forming a J-shaped curve.

• Logistic Growth: Population growth slows as it approaches carrying capacity (K), forming an S-shaped curve.

Equations:

• Exponential growth: $\frac{dN}{dt} = rN$

• Logistic growth: $\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$

Life History Traits

• Traits that affect reproduction and survival, such as age at first reproduction, number of offspring, and parental care.

Human Population Growth

• Human population has grown exponentially but is now slowing in some regions.

• Demographic Transition: Shift from high birth and death rates to low birth and death rates as a country develops.

Chapter 52 – Ecology and the Biosphere

Ecology and Biomes

• Ecology: The study of interactions between organisms and their environment.

• Biomes: Major life zones characterized by vegetation type (terrestrial) or physical environment (aquatic).

• Climate (temperature and precipitation) is the primary factor determining biome distribution.

Global Climate Patterns

• Sunlight intensity, Earth's tilt, and rotation create global climate patterns.

• Seasonal variation is caused by Earth's axial tilt.

Seasonal Turnover in Lakes

• In temperate lakes, seasonal turnover redistributes oxygen and nutrients, supporting aquatic life.

Chapter 54 – Community Ecology

Species Interactions

• Types of Interactions: Parasitism, predation, mutualism, commensalism.

• Ecological Niche: The sum of a species' use of biotic and abiotic resources.

• Fundamental Niche: The potential niche a species could occupy.

• Realized Niche: The niche a species actually occupies due to competition.

Competition and Resource Partitioning

• Competitive Exclusion Principle: Two species competing for the same resources cannot coexist indefinitely.

• Resource Partitioning: Differentiation of niches that enables similar species to coexist.

Mimicry

• Batesian Mimicry: A harmless species mimics a harmful one.

• Müllerian Mimicry: Two or more harmful species resemble each other.

Keystone Species and Trophic Cascades

• Keystone Species: Species that have a disproportionately large effect on community structure.

• Trophic Cascade: A process in which effects on one trophic level cascade to other levels (e.g., wolves in Yellowstone).

Chapter 55 – Ecosystems

Energy Flow and Trophic Levels

• Energy transfer between trophic levels is inefficient; about 10% of energy is passed to the next level.

• Trophic Levels: Producers (plants), primary consumers (herbivores), secondary consumers (carnivores), etc.

• Most energy is lost as heat due to metabolism.

Food Chains and Food Webs

• Food chains show linear energy flow; food webs show complex feeding relationships.

• Shorter food chains are more efficient; longer chains lose more energy.

Biogeochemical Cycles

• Carbon Cycle: Carbon is cycled globally through photosynthesis and respiration.

• Phosphorus and Potassium: These are recycled locally in ecosystems.

• Biological Magnification: Toxins become more concentrated in higher trophic levels.

Concept Check Questions

• Be able to answer questions on population growth, survivorship curves, energy transfer, and keystone species.

Summary Table: Types of Species Interactions

Interaction Type	Effect on Species 1	Effect on Species 2	Example
Predation	+	-	Lion and zebra
Parasitism	+	-	Tapeworm in human
Mutualism	+	+	Bees and flowers
Commensalism	+	0	Barnacles on whales
Competition	-	-	Two bird species for same nest site

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard General Biology curriculum.