UNG Ecology Midterm

Biology

The scientific study of life and living organisms.

Hierarchical Organization of Life

The levels of biological organization structured from smallest to largest: Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere.

Studying Biology (Reductionism vs. Emergent Properties)

Reductionism breaks complex systems down into simpler components to study them, while the emergent properties approach looks at how novel properties arise at higher levels of organization that weren't present at lower levels.

7 Properties of Life

The characteristics shared by all living organisms:

Order,

Adaptation,

Response to the Environment,

Regulation (Homeostasis),

Energy Processing,

Growth and Development,

and Reproduction.

Three Domains of Life

Bacteria (prokaryotic),

Archaea (prokaryotic, often extremophiles),

and Eukarya (all eukaryotic organisms).

Core Theme of Biology

Evolution; it explains both the unity (kinship from common ancestry) and diversity (adaptations to different environments) of all living organisms.

Ecology

A subdiscipline of biological science that studies the interactions between organisms and their physical and chemical environment.

Scientific Method Steps

An organized approach to solving a problem: Observation → Question → Hypothesis → Prediction → Experiment/Testing → Analyze Results → Conclusion.

Hypothesis

A tentative, testable, and falsifiable explanation for a specific, narrow set of observations.

Scientific Theory

A broad, comprehensive, and well-supported explanation for a natural phenomenon that is backed by a massive body of evidence and can generate new hypotheses.

Assessing Scientific Credibility

Evaluating sources based on peer review, institutional reputation, potential conflicts of interest, and replication of results by other scientists.

Evolution

The change in the genetic composition (allele frequencies) of a population over successive generations; descent with modification.

Jean-Baptiste Lamarck

An early evolutionary thinker who proposed the (later disproven) theory of inheritance of acquired characteristics, suggesting organisms change during their lifetime based on use/disuse and pass those traits to offspring.

Charles Darwin & Alfred Russel Wallace

Co-discoverers of the theory of evolution by natural selection, publishing their ideas around the same time (1858–1859).

Natural Selection

The mechanism of evolution where individuals with inherited traits better suited to their environment survive and reproduce at higher rates than other individuals.

Three Conditions for Natural Selection

1. Variation in traits within a population.

2. Heritability of those traits.

3. Differential reproductive success (more offspring are produced than can survive, leading to competition).

Evidence for Evolution: Direct Observations

Real-time documentation of evolutionary change, such as the rapid evolution of antibiotic resistance in bacteria or beak size changes in Darwin’s finches during droughts.

Evidence for Evolution: The Fossil Record

The physical remains or traces of past life showing a chronological progression of anatomical changes and transitional forms (e.g., Tiktaalik bridging fish and tetrapods).

Evidence for Evolution: Biogeography

The geographic distribution of species across the planet, which reflects their evolutionary history (e.g., unique marsupial diversification in isolated Australia).

Homology

Anatomical, molecular, or developmental similarities in different species that exist because they were inherited from a common ancestor (e.g., the forelimbs of humans, bats, and whales).

Adaptation

An inherited characteristic or trait that enhances an organism's ability to survive and reproduce in a specific environment (e.g., camel humps for fat storage).

Misconception: Evolution is "just a theory"

Critique: In everyday speech, "theory" means a guess. In science, a theory is a rigorously tested, widely accepted framework supported by massive empirical evidence.

Misconception: Individuals evolve

Critique: Individual organisms do not evolve during their lifetimes their genetic makeup stays the same. Populations evolve over generations as allele frequencies shift.

Microevolution

Evolutionary change on its smallest scale, defined as a change in allele frequencies in a population over generations.

Role of the Environment in Microevolution

The environment acts as the selective pressure that determines which phenotypes (and underlying alleles) are advantageous, neutral, or deleterious, steering the trajectory of the population.

Allele Frequency Formula

The proportion of a specific allele among all allele copies at a given locus in a population: p + q = 1

Genotypic Frequency Formula

The proportion of a specific genotype in a population, modeled by the Hardy-Weinberg expansion: p^2 + 2pq + q^2 = 1

Hardy-Weinberg Principle

A mathematical model stating that allele and genotype frequencies in a population will remain constant (in equilibrium) from generation to generation in the absence of evolutionary forces.

Hardy-Weinberg Application

By comparing a real population's genotypic frequencies to the expected Hardy-Weinberg values, scientists can detect whether evolutionary forces are actively at work.

5 Assumptions of Hardy-Weinberg Equilibrium

1. No mutations.

2. Random mating.

3. No natural selection.

4. Extremely large population size (no genetic drift).

5. No gene flow (immigration/emigration).

Mechanism of Evolution: Mutation

A permanent change in the DNA sequence it is the ultimate source of all new genetic variation.

Mechanism of Evolution: Genetic Drift

Random fluctuations in allele frequencies from one generation to the next due to chance events, which has a much stronger impact in small populations.

Bottleneck Effect

A type of genetic drift that occurs when a severe, random drop in population size (e.g., from a natural disaster) leaves a small surviving group with a drastically reduced genetic diversity compared to the original population.

Founder Effect

A type of genetic drift that occurs when a few individuals become isolated from a larger population and establish a new colony, whose gene pool does not reflect the genetic diversity of the source population.

Mechanism of Evolution: Gene Flow

The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes (migration), which tends to reduce genetic differences between populations over time.

Directional Selection

A mode of natural selection that shifts the overall makeup of the population by favoring individuals at one extreme of a phenotypic distribution.

Disruptive (Diversifying) Selection

A mode of natural selection that favors individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes.

Stabilizing Selection

A mode of natural selection that favors intermediate variants by acting against extreme phenotypes, maintaining the status quo.

Biological Species Concept

Defines a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but cannot do so with members of other such groups.

Prezygotic Barriers

Reproductive isolation mechanisms that prevent mating or hinder fertilization if mating does occur (e.g., habitat, temporal, behavioral, mechanical, or gametic isolation).

Postzygotic Barriers

Reproductive isolation mechanisms that prevent a hybrid zygote from developing into a viable, fertile adult (e.g., reduced hybrid viability, reduced hybrid fertility, or hybrid breakdown).

Adaptive Radiation

A process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available or opens new ecological niches (e.g., Darwin's finches).

Allopatric Speciation

The formation of new species from geographically isolated populations due to a physical barrier (e.g., a river, mountain range, or glacier) that prevents gene flow.

Sympatric Speciation

The formation of new species within populations that inhabit the same geographic area, often driven by polyploidy, sexual selection, or habitat differentiation.

Gradual Speciation Model

The view that species change and diverge slowly, steadily, and incrementally over long stretches of geological time.

Punctuated Equilibrium Model

The view that evolution consists of long periods of apparent stasis (no change) interrupted by brief, rapid bursts of sudden evolutionary change and speciation.

Bacteria vs. Archaea

While both are single-celled prokaryotes, Bacteria have cell walls made of peptidoglycan and use unbranched fatty acids in their membranes. Archaea lack peptidoglycan, have unique branched membrane lipids, possess RNA polymerases closer to eukaryotes, and often live in extreme environments.

Prokaryotic Structural Features

They lack a membrane-bound nucleus and membrane-bound organelles. They feature a nucleoid region with a circular DNA chromosome, ribosomes, a cell wall, and may have capsules, fimbriae, or flagella.

Prokaryotic Reproduction: Binary Fission

An asexual method of reproduction where a single prokaryotic cell replicates its DNA and divides into two identical clone cells.

Prokaryotic Genetic Recombination Mechanisms

Because they reproduce horizontally, they gain diversity via: Transformation (absorbing foreign DNA from the environment), Transduction (viral transfer via bacteriophages), and Conjugation (direct plasmid transfer between cells).

Bacterial and Archaeal Phyla Characteristics

Bacterial phyla (e.g., Cyanobacteria: photosynthetic; proteobacteria: diverse Gram-negative metabolic groups) and Archaea phyla (e.g., Euryarchaeota: includes methanogens and halophiles; crenarchaeota: mostly thermophiles) show incredible biochemical diversity.

Endosymbiotic Theory

The hypothesis that eukaryotic cells evolved when an ancestral archaeal-like cell engulfed an aerobic bacterium (which became the mitochondrion) and later a photosynthetic bacterium (which became the chloroplast).

Ecological Roles of Prokaryotes

They act as decomposers recycling nutrients, fix atmospheric nitrogen (N2 > NH3) for plant use, and engage in vital symbiotic relationships (such as gut microbiota).

Prokaryotes and Disease Mechanisms

Pathogenic bacteria cause disease primarily by producing toxins: Exotoxins (proteins secreted by living bacteria) and Endotoxins (lipopolysaccharide components of the outer membrane released when the cell dies).

Zoonosis and Disease Transmission

The complex interaction where pathogens circulate among animals, humans, and vectors within shared environments, allowing diseases to jump species barriers due to ecological disruption or close contact.

Evolution of Antibiotic Resistance

Occurs via natural selection: when an antibiotic is used, susceptible bacteria are killed, leaving behind rare individuals with mutant, resistant alleles. These survivors multiply, rapidly dominating the population.

Unique Features of Animals

They are multicellular, heterotrophic eukaryotes that ingest their food, lack cell walls (relying on structural proteins like collagen), and typically possess specialized nervous and muscular tissues.

Animal Classification: Symmetry

Morphological sorting based on body plan: Radial symmetry (top/bottom, but no front/back or left/right) vs. Bilateral symmetry (two-sided symmetry with a distinct head/anterior and tail/posterior).

Animal Classification: Embryonic Development

Classification based on tissue layers (Diploblastic vs. Triploblastic) and the fate of the blastopore: Protostomes (blastopore becomes the mouth) vs. Deuterostomes (blastopore becomes the anus).

Cambrian Explosion

A geological era roughly 530 million years ago characterized by a rapid wave of diversification, giving rise to the first major body plans and ancestors of most modern animal phyla.

Porifera

Sponges: Asymmetrical, sessile invertebrates that lack true tissues; they are filter feeders with specialized cells called choanocytes.

Cnidaria

(Jellies, Corals, Anemones) Radially symmetrical, diploblastic animals with a gastrovascular cavity and specialized stinging cells called cnidocytes.

Platyhelminthes

(Flatworms) Bilaterally symmetrical, triploblastic, acoelomate (lacking a body cavity) unsegmented worms.

Mollusca

(Snails, Clams, Octopuses) Coelomate invertebrates with a soft body, typically divided into a muscular foot, a visceral mass, and a mantle that may secrete a hard calcium carbonate shell.

Annelida

(Segmented Worms) Coelomates characterized by a distinguished ring-like segmentation of their body wall and internal organs (e.g., earthworms, leeches).

Nematoda

(Roundworms) Pseudocoelomate, unsegmented worms covered by a tough cuticle that they must shed (ecdysis) as they grow.

Arthropoda

(Insects, Spiders, Crustaceans) The largest animal phylum, characterized by a chitinous exoskeleton, segmented bodies, and jointed appendages.

Echinodermata

(Sea Stars, Sea Urchins) Deuterostome coelomates with a water vascular system used for locomotion and feeding; adults show secondary radial symmetry, while larvae are bilateral.

4 Derived Characters of Chordates

Traits present in all chordates at some point during development:

1. Notochord.

2. Dorsal, hollow nerve cord.

3. Pharyngeal slits or clefts.

4. Muscular, post-anal tail.

Fish Phylogeny Progression

Evolved from jawless forms (Agnathans like hagfishes/lampreys) to cartilaginous jawed fish (Chondrichthyes like sharks) to bony fishes (Osteichthyes), which include ray-finned fish and lobe-finned fish.

Evolution of Tetrapods

Lobe-finned fishes with fleshy, muscular pectoral and pelvic fins transitioned to life on land, evolving into the first four-limbed vertebrates (tetrapods) during the Devonian period.

Amphibians

The earliest tetrapods; they possess moist, permeable skin used for gas exchange and remain tied to aquatic environments for reproduction because their eggs lack a protective shell.

Reptiles & The Amniotic Egg

Reptiles are amniotes (possessing an egg with specialized extraembryonic membranes that protect the embryo), allowing them to break dependency on water and complete their life cycle entirely on dry land.

Birds (Aves)

Endothermic reptiles adapted for flight, possessing feathers (modified scales), hollow bones, and a highly efficient respiratory system; they are cladistically categorized as the sole surviving lineage of theropod dinosaurs.

Mammalian Derived Characteristics

Mammary glands (which produce milk), hair or fur, specialized differentiated teeth, and endothermy.

Mammalian Evolution from Synapsids

Mammals evolved from a lineage of amniotes called synapsids, characterized by a single temporal fenestra (opening) behind the eye socket, which diversified heavily after the Permian extinction.

Hominin Evolution and Environment

The evolutionary branch of apes that includes modern humans and our extinct bipedal ancestors. Environmental changes in Africa (drier climates turning dense forests into open savannas) favored the evolution of bipedalism, tool use, and larger brains.

Out of Africa Migration Waves

Genus Homo expanded in waves: Homo erectus was the first to migrate out of Africa into Eurasia. Later, Homo sapiens emerged in Africa and migrated globally in a subsequent, more dominant wave, replacing or absorbing existing hominin groups.

Hominin Interbreeding Evidence

Genomic data confirms that early Homo sapiens interbred with other contemporaneous Homo species, leaving traces of Neanderthal and Denisovan DNA in the genomes of modern non-African human populations.

Levels of Ecological Organization

The scale of ecological study from narrowest to broadest: Organismal Ecology → Population Ecology → Community Ecology → Ecosystem Ecology → Landscape Ecology → Global Ecology (Biosphere).

Abiotic vs. Biotic Factors

Abiotic factors are non-living physical and chemical components of an environment (e.g., temperature, sunlight, water, soil nutrients).

Biotic factors are the living components of an environment (e.g., competitors, predators, prey, parasites).

Global Species Distribution Patterns

The distribution of life is determined by how abiotic limits (like temperature tolerances) and biotic interactions (like competitive exclusion or predation) intersect across geography.

Terrestrial Biomes

Major life zones categorized by their vegetation type, which is primarily determined by regional climate patterns—specifically annual mean temperature and precipitation.

Tropical Rainforest

A biome characterized by high year-round temperatures and rainfall, supporting the highest biodiversity of any terrestrial biome, with dense, layered vertical vegetation.

Desert

A biome characterized by extremely low, unpredictable precipitation (typically less than 30 cm per year) and vegetation adapted for water conservation (like succulents).

Savanna

A tropical grassland biome with warm year-round temperatures, a pronounced dry season, scattered individual trees, and frequent fires.

Chaparral

A coastal scrubland biome featuring mild, rainy winters and hot, dry summers, dominated by drought-resistant shrubs adapted to periodic wild fires.

Temperate Grassland

A biome dominated by grasses, featuring cold winters and hot summers, with fertile soils maintained by seasonal droughts and periodic fires.

Temperate Broadleaf Forest

A biome found in mid-latitudes with distinct four seasons, significant moisture, and dominated by deciduous trees that drop their leaves in autumn.

Northern Coniferous Forest (Taiga)

The largest terrestrial biome, characterized by long, cold winters and short, wet summers, dominated by cone-bearing evergreen trees (conifers).

Tundra

An expansive Arctic/alpine biome featuring extremely low temperatures, high winds, and a layer of permanently frozen subsoil called permafrost, restricting vegetation to low-growing mosses, lichens, and shrubs.

What is the classification of species from most inclusive to least inclusive?

1. Domain

2. Kingdom

3. Phylum

4. Class

5. Order

6. Family

7. Genus

8. Species