Preliminary Biology Study Notes – Key Terms (Cells, Transport, Plant Biology, Evolution, Ecosystems)

A vocabulary-style set of flashcards covering core concepts from cell biology, cell transport, plant biology, evolution, and ecosystem dynamics as presented in the notes.

Prokaryote

A microorganism that lacks a nucleus and membrane-bound organelles; DNA is circular and naked; 70S ribosomes; usually smaller (1–5 μm); reproduces by binary fission.

Eukaryote

Organism with membrane-bound organelles and a nucleus; DNA is linear and associated with proteins; 80S ribosomes; larger (10–100 μm); reproduces by mitosis and meiosis.

DNA in Prokaryotes

DNA is naked and circular; not enclosed by a nucleus.

DNA in Eukaryotes

DNA is bound to proteins (histones) and linear, with introns present.

Nucleus

Membrane-bound organelle that houses DNA and controls cellular activities.

70S Ribosomes

Ribosomes typical of prokaryotes; smaller than eukaryotic ribosomes.

80S Ribosomes

Ribosomes typical of eukaryotes; larger than prokaryotic ribosomes.

Nucleus vs No Nucleus

Eukaryotes have a nucleus; prokaryotes do not.

Membrane-bound Organelles

Organelles enclosed by membranes (e.g., mitochondria, chloroplasts, ER, Golgi) found in eukaryotic cells.

Prokaryotes Examples

Bacteria and Archaea.

Eukaryotes Examples

Animals, plants, fungi, and protists.

Cell Size Comparison

Prokaryotic cells are generally smaller; eukaryotic cells are larger.

Cell Wall (Prokaryotes)

Often present; supports and protects the cell; composed of peptidoglycan in bacteria.

Cell Wall (Eukaryotes)

Present in plants, fungi, and some protists; cellulose in plants, chitin in fungi.

Pili

Hair-like structures on some prokaryotes that aid adhesion.

Flagella

Whip-like tails that provide locomotion in some prokaryotes and eukaryotes.

Capsule

A protective outer layer in some bacteria made of complex carbohydrates.

Bacterial Chromosome

Large circular DNA molecule; may include plasmids (smaller rings of DNA).

Plasmids

Small circular DNA molecules in bacteria that can carry extra genes.

Rocks and Organelle Comparison: Prokaryotic vs Eukaryotic

Prokaryotes: no nucleus, no membrane-bound organelles, 70S ribosomes; Eukaryotes: nucleus, membrane-bound organelles, 80S ribosomes.

Mitosis

Nuclear division that results in two genetically identical diploid daughter cells (in many organisms).

Meiosis

Nuclear division producing four genetically diverse haploid gametes.

Binary Fission

A simple prokaryotic cell division process producing two identical cells.

Diploid vs Haploid

Diploid (2n) has paired chromosomes; haploid (n) has a single set of chromosomes.

Size Range (Prokaryotes)

Approximately 0.1–5.0 μm.

Size Range (Eukaryotes)

Approximately 10–100 μm.

Organelles

Membrane-bound structures inside eukaryotic cells with specialized functions.

Nucleolus

A region within the nucleus where ribosomal RNA (rRNA) synthesis occurs.

Chloroplasts

Plant/ algal organelles where photosynthesis occurs; contain chlorophyll and thylakoids.

Mitochondria

Organelles that generate ATP through cellular respiration.

Rough Endoplasmic Reticulum (RER)

ER studded with ribosomes; synthesizes and transports proteins.

Smooth Endoplasmic Reticulum (SER)

ER lacking ribosomes; synthesizes lipids and processes toxins.

Golgi Body

Modifies, sorts, and packages proteins and lipids into vesicles.

Lysosome

Digestive organelle containing enzymes for waste processing.

Vacuole

Fluid-filled organelle; stores nutrients and wastes; large central vacuole in plants.

Ribosomes (Cell Type Difference)

Ribosomes synthesize proteins; 70S in prokaryotes, 80S in eukaryotes.

Cytoplasm

Jelly-like fluid inside cells where organelles reside and metabolic reactions occur.

Cytoskeleton

Network of protein filaments providing structure, transport, and movement.

Centrosome

Organelle organizing microtubules during cell division (animal cells).

Membrane Structure: Fluid Mosaic Model

Cell membrane as a lipid bilayer with floating proteins; lipids form a fluid, dynamic sea.

Phospholipid Bilayer

Two layers of phospholipids with hydrophilic heads and hydrophobic tails.

Amphipathic

Molecules having both hydrophilic and hydrophobic regions.

Cholesterol in Membranes

Lipid that increases membrane flexibility and stability in animals.

Membrane Proteins (Types)

Integral, transmembrane, peripheral proteins that perform transport, signaling, and structural roles.

Glycoproteins & Glycolipids

Carbohydrate groups attached to proteins/lipids on the outer surface for cell recognition.

Carrier Proteins

Proteins that bind to substrates and shuttle them across membranes.

Ion Channels

Proteins forming pores that ions pass through, often gated.

Aquaporins

Channel proteins that facilitate water diffusion across membranes.

Diffusion

Passive movement of molecules from high to low concentration without energy input.

Facilitated Diffusion

Diffusion of large or charged molecules via carrier proteins or channels.

Osmosis

Diffusion of water across a semipermeable membrane from high to low water potential.

Isotonic / Hypotonic / Hypertonic

Isotonic: equal solute; Hypotonic: lower solute outside; Hypertonic: higher solute outside.

Active Transport

Energy-requiring movement of substances against their gradient, usually via ATP and carrier proteins.

Endocytosis

Enclosure of material by the cell membrane to bring substances into the cell.

Exocytosis

Vesicles fuse with the cell membrane to release substances outside the cell.

Mitochondria and Cellular Respiration

Mitochondria generate ATP by oxidizing glucose and other fuels.

Chloroplasts and Photosynthesis

Chloroplasts capture light energy to convert CO2 and water into glucose and O2.

Grana and Stroma

Grana: stacks of thylakoid membranes; Stroma: fluid surrounding; sites of light-dependent and light-independent reactions respectively.

Nucleus Functions

Houses DNA, controls cellular activities, and regulates gene expression.

RER vs SER Functions

RER synthesizes proteins; SER synthesizes lipids and processes toxins.

Endomembrane System

Interconnected system of membranes within the cell (ER, Golgi, vesicles) for protein/lipid trafficking.

Plant Cell Vacuole (Tonoplast)

Large central vacuole that maintains turgor pressure and stores substances.

Plant Cell Wall vs Animal Cell Membrane

Plant cells have rigid cell walls; animal cells rely on flexible plasma membranes.

Stomata & Guard Cells

Stomata regulate gas exchange and water loss; guard cells control opening/closing.

Xylem

Dead, lignified vascular tissue that transports water and minerals from roots to shoots unidirectionally.

Phloem

Vascular tissue that transports sugars (via translocation) in a bidirectional flow.

Translocation / Pressure Flow

Phloem sap movement from sources to sinks driven by pressure differences.

Source-to-Sink Concept

Sugar produced in leaves (source) is moved to growing tissues or storage (sink) via phloem.

Root Hairs

Extensions of root epidermal cells increasing surface area for water/mineral uptake.

Gas Exchange in Animals vs Plants

Animals exchange gases via lungs, skin, gills; plants via stomata and leaf mesophyll.

Alveoli

Air-filled sacs in lungs where gas exchange with capillaries occurs.

Arteries / Capillaries / Veins

Arteries carry blood away from the heart; capillaries enable exchange; veins return blood.

Open vs Closed Circulatory Systems

Open: body fluids mix with hemolymph; Closed: blood circulates in closed vessels.

Blood Components

Red blood cells (carry O2/CO2), white blood cells (defense), platelets (clotting), plasma (fluid).

Biotic vs Abiotic Factors

Biotic: living components; Abiotic: non-living physical/chemical factors.

Predation

Predator-prey interaction; predator affects prey population dynamics.

Competition (Intra-/Interspecific)

Intraspecific: within species; Interspecific: between species; can drive niche differentiation.

Allelopathy

Chemical inhibition of one species by another, affecting nearby plant growth.

Symbiosis (Mutualism/Commensalism/Parasitism)

Interactions where two species live closely; mutualism both benefit, commensalism one benefits, parasitism one benefits at the other’s expense.

Niche & Competitive Exclusion

Niche: role and resources used by a species; no two species can occupy the exact niche.

Evolution by Natural Selection

Variation exists; more offspring than can survive; environment creates selection pressures; favorable traits become more common.

Convergent Evolution

Unrelated species independently evolve similar traits due to similar environments.

Divergent Evolution

Related species evolve different traits due to different environments or niches.

Adaptive Radiation

Diversification of a lineage into a variety of new forms to occupy different niches.

Punctuated Equilibrium

Evolution in rapid bursts separated by long periods of stability.

Gradualism

Slow, continuous evolution with gradual accumulation of small changes.

Homologous Structures

Similar structures with shared ancestry; evidence of divergent evolution.

Analogous Structures

Similar function but different origins; evidence of convergent evolution.

Vestigial Structures

Remnants of features once useful in ancestors; current function may be reduced or absent.

Comparative Embryology

Developmental similarities among related species providing clues to ancestry.

Biogeography

Geographical distribution of species; supports isolation and adaptive radiation.

Fossils & Relative Dating

Fossils preserve past life; relative dating uses strata to infer order of events (superposition, stratigraphy).

Biostratigraphy

Dating using index fossils to define geological periods.

Paleomagnetism

Dating via ancient magnetic field orientation recorded in rocks.

Absolute Dating

Determining exact ages using radioactive decay (e.g., carbon-14 dating).

Radiometric Dating

Dating by measuring decay of radioactive isotopes to estimate age.

Amino Acid Sequencing (Cytochrome-c)

Comparing amino acid sequences to infer relatedness among species.

Marsupials vs Placentals vs Monotremes

Marsupials: short gestation, pouches; Placentals: longer gestation; Monotremes: egg-laying.

Stems: Sclerophylls

Woody, tough-leaved plants adapted to arid, fire-prone environments (e.g., eucalyptus).

Stromatolites

Layered mounds formed by cyanobacteria; key for understanding early life and oxygenation of the atmosphere.