LC

1407_Exam_3_Review Question & Answer

Producers

  • Definition: Organisms that synthesize their own organic molecules (sugars, amino acids, lipids) from inorganic raw materials and an external energy source.
    • Energy sources: light (photosynthesis) or chemical bond energy (chemosynthesis).
  • Primary ecological role: Form the base of almost every food web, converting abiotic energy into biologically usable chemical energy.
  • Classic examples
    • Terrestrial: green plants (angiosperms, gymnosperms), mosses, liverworts.
    • Aquatic: algae (green, red, brown), cyanobacteria, phytoplankton.
    • Extreme environments: chemolithoautotrophic Archaea at hydrothermal vents.

Modes of Autotrophy

  • Photoautotroph
    • Use light energy + CO2 + H2O to produce C6H{12}O6 (+ O2 as a by-product).
    • Pigments: chlorophyll a & b (plants, green algae), bacteriochlorophyll (purple bacteria), phycobilins (cyanobacteria, red algae).
    • Significance: responsible for ‘oxygenic’ photosynthesis that generated Earth’s oxygen atmosphere.
  • Chemoautotroph
    • Energy from inorganic redox reactions (e.g., NH3\rightarrow NO2^-, H_2S\rightarrow S, Fe^{2+}\rightarrow Fe^{3+}).
    • Typical habitats: deep-sea vents, caves, acidic mine drainage.
    • Ecological importance: primary producers in ecosystems without sunlight; drive global nitrogen & sulfur cycles.

Phytoplankton

  • Microscopic, free-floating, photosynthetic organisms in aquatic systems.
    • Include cyanobacteria, diatoms (Bacillariophyta), dinoflagellates, coccolithophores.
  • Account for ≈50\% of global primary production; major oxygen producers.
  • Population dynamics tightly linked to nutrient availability (nitrate, phosphate, silicate) & light.

Red Tide

  • Common term for harmful algal blooms (HABs) caused mainly by toxin-producing dinoflagellates.
  • Pigments (peridinin, carotenoids) can turn water reddish-brown.
  • Impacts
    • Release neurotoxins (saxitoxin, brevetoxin) → fish kills, paralytic shellfish poisoning in humans.
    • Economic: fishery & tourism losses.
  • Triggers: excess nutrients (agricultural runoff), warm/stagnant water, stratification.

Major Groups / Phyla of Micro Producers (focus)

  • Cyanobacteria (Phylum Cyanobacteria)
    • Prokaryotic; chlorophyll a & phycobilin pigments; some fix atmospheric N_2 in heterocysts.
  • Bacillariophyta (Diatoms)
    • Silica (glass) frustule in two halves; radial or bilateral symmetry; primary marine producers; store oil → important fossil fuel source (diatomaceous earth).
  • Dinoflagellata (Dinoflagellates)
    • Two perpendicular flagella; cellulose plates (theca); many bioluminescent; some mixotrophic; HAB agents.
  • Euglenophyta (Euglenoids)
    • Pellicle (protein strips) instead of cell wall; single emergent flagellum; eye-spot; facultative heterotrophs.
  • Chlorophyta (Green algae)
    • Cellulose wall, chlorophyll a/b; ancestral group to land plants; unicells (Chlamydomonas) → colonies (Volvox) → multicellular (Ulva).
  • Rhodophyta (Red algae) – mostly macroalgae but some microscopic; phycoerythrin gives red color; important coral reef builders (coralline algae).

Algal Symbioses (2 key examples)

  1. Zooxanthellae–Coral Symbiosis
    • Dinoflagellates (genus Symbiodinium) live inside coral endoderm; provide \approx90\% of coral’s energy via photosynthate.
    • Coral provides shelter & CO_2; breakdown leads to coral bleaching.
  2. Lichens
    • Mutualism between fungus (usually Ascomycete) & photosynthetic partner (green alga ≈90\% cases, cyanobacterium in \approx10\%).
    • Pioneer species on bare rock; bioindicators of air quality.

Algal Blooms ⇄ Dead Zones

  • Bloom: explosive algal population growth driven by nutrient loading (nitrate, phosphate) → “eutrophication”.
  • Death & decomposition of algae consume dissolved O_2 via aerobic bacteria.
  • Result: hypoxia (O_2<2\,mg\,L^{-1}) → “dead zone”; mobile fauna flee, benthic organisms die.
  • Causes: agricultural runoff, sewage effluent, atmospheric deposition, stratified warm waters (reduced mixing).
    • Famous case: Gulf of Mexico dead zone (>20,000 km²).

Early Land Plants – Two Broad Categories

  1. Non-vascular Bryophytes
    • Liverworts (Hepatophyta), Hornworts (Anthocerophyta), Mosses (Bryophyta).
    • Dominant gametophyte; no true vascular tissue; water-dependent reproduction (flagellated sperm); produce peat deposits (mainly Sphagnum mosses).
  2. Seedless Vascular Plants
    • Lycophytes (club mosses, quillworts) & Monilophytes (ferns, horsetails, whisk ferns).
    • Dominant sporophyte; true xylem & phloem; microphylls (lycophytes) vs megaphylls (others); formed Carboniferous coal forests.

Key Terms & Concepts

  • Peat: partially decayed organic matter in waterlogged, anaerobic bogs; high carbon storage; harvested for fuel & horticulture.
  • Homosporous vs Heterosporous
    • Homosporous: one spore type → bisexual gametophyte (most ferns, bryophytes).
    • Heterosporous: microspores (♂) & megaspores (♀) → precursor to seeds (some lycophytes, all seed plants).
  • Xylem: vascular tissue of dead, lignified tracheary elements (tracheids, vessel elements) conducting water & minerals root→shoot via transpiration pull and cohesion-tension.
  • Phloem: living sieve tube elements + companion cells; translocates sugars \text{(source→sink)} via pressure-flow mechanism.
  • Meristems: perpetually embryonic tissues where cell division occurs.
    • Apical (primary growth); lateral – vascular cambium & cork cambium (secondary growth).
  • Alternation of Generations
    • Regular life-cycle alternation between multicellular haploid gametophyte (n) and multicellular diploid sporophyte (2n).

Organ Modifications

  • Roots
    • Storage (carrot, beet), Prop (mangrove), Pneumatophores (submerged roots for gas), Haustoria (parasitic mistletoe).
  • Stems
    • Rhizome (ginger), Stolon/Runner (strawberry), Tuber (potato), Cactus cladode (photosynthetic stem).
  • Leaves
    • Tendrils (peas), Spines (cacti), Storage succulence (aloe), Insect traps (pitcher plant, Venus flytrap), Bracts (poinsettia).

Buds: Apical vs Axillary

  • Apical (terminal) bud: tip of shoot; elongation; produces auxin that enforces apical dominance (suppresses lateral branching).
  • Axillary bud: node between leaf & stem; potential to form branch, flower, or thorn when apical dominance relieved (pruning, damage).

Primary vs Secondary Growth

  • Primary Growth
    • Lengthening of roots & shoots via apical meristems; tissues: primary xylem, primary phloem, epidermis, ground tissue (pith, cortex).
  • Secondary Growth
    • Increase in girth; tissues from lateral meristems:
    • Vascular cambium → secondary xylem (wood) inward, secondary phloem outward.
    • Cork cambium → periderm (cork + cork cambium + phelloderm) replacing epidermis.

Parasitic vs Carnivorous Plants

  • Parasitic: obtain water, minerals, & sometimes photosynthate from host via haustoria (dodder, mistletoe, Rafflesia). May be holoparasites (non-photosynthetic) or hemiparasites (retain some photosynthesis).
  • Carnivorous: photosynthetic but supplement N & P by digesting animals; evolve in nutrient-poor, acidic soils (e.g., pitcher plants, sundews). Enzymatic or bacterial digestion in specialized leaf traps.

Crop Rotation

  • Practice of alternating crop species on the same land across seasons/years.
    • E.g., corn (heavy N user) → soybean (legume N_2-fixer).
  • Benefits
    • Maintains soil fertility, breaks pest & pathogen cycles, reduces need for synthetic fertilizers, improves soil structure.
  • Historical significance: four-field system (wheat, turnips, barley, clover) boosted European agriculture.

Types of Heterotrophs

  • Herbivore: plant-eating (deer, cows).
  • Carnivore: animal-eating (lions, sharks).
  • Omnivore: plant & animal diet (humans, bears).
  • Detritivore: ingest detritus (earthworms).
  • Decomposer/Saprotroph: extracellular digestion of dead matter (fungi, many bacteria).
  • Parasite: live on/in host, harming it (tapeworm).

Major Invertebrate Groups & Key Characteristics

  • Porifera (Sponges): choanocyte feeding; no true tissues; spicules.
  • Cnidaria: radial symmetry; cnidocytes; diploblastic; polyp & medusa.
  • Platyhelminthes (Flatworms): acoelomate; dorsoventrally flattened; many parasitic (tapeworms, flukes).
  • Nematoda (Roundworms): pseudocoelomate; unsegmented; cuticle; e.g., Ascaris, hookworm.
  • Annelida: segmented coelomate worms; setae; closed circulation (earthworms, leeches).
  • Mollusca: mantle, muscular foot, radula; classes – Gastropoda, Bivalvia, Cephalopoda.
  • Arthropoda: jointed appendages, exoskeleton (chitin), segmented; subphyla Chelicerata, Myriapoda, Crustacea, Hexapoda.
  • Echinodermata: pentaradial adult symmetry; water vascular system; endoskeleton of ossicles (sea stars, urchins).

Symmetry

  • Radial Symmetry: any plane through central axis → mirror halves (cnidarians, adult echinoderms). Adaptive for sessile/drifting feeders.
  • Bilateral Symmetry: single sagittal plane; cephalization; correlated with active movement & directed sensory organs.

Body Cavity (Coelom)

  • Fluid/air-filled space between digestive tract & body wall.
    • Acoelomate (no cavity), Pseudocoelomate (partial mesoderm lining), Coelomate (complete mesoderm lining).
  • Functions: organ cushioning, hydrostatic skeleton, independent organ movement, circulatory distribution.

Parasitic Animals (review examples)

  • Platyhelminthes: Schistosoma (blood fluke), Taenia (beef/pork tapeworm).
  • Nematoda: Ascaris, Trichinella, Wuchereria (elephantiasis), Enterobius (pinworm).
  • Annelida: Hirudo medicinalis (medicinal leech – ectoparasite).
  • Arthropoda: ticks (Lyme disease), lice.

Vertebrate Groups & Core Traits

  • Agnatha (Jawless fish): lampreys, hagfish; cartilage skeleton; no paired fins.
  • Chondrichthyes (Cartilaginous fish): sharks, rays; placoid scales; oil-filled liver for buoyancy.
  • Osteichthyes (Bony fish): ossified skeleton; swim bladder; operculum.
  • Amphibia: tied to water for reproduction; permeable skin; 3-chamber heart (frogs, salamanders).
  • Reptilia (incl. birds = debate): keratin scales, shelled amniotic egg; ectothermic except birds.
  • Aves (Birds): feathers, hollow bones, endothermic, 4-chamber heart.
  • Mammalia: hair, mammary glands, differentiated teeth, endothermic; subclasses monotremes, marsupials, eutherians.

Reproductive & Thermal Strategies

  • Oviparous: eggs laid outside; embryo nourished by yolk (most fish, amphibians, reptiles, monotremes, birds).
  • Ovoviviparous: eggs retained inside; hatch internally; no placental connection (some sharks, snakes).
  • Viviparous: young develop in uterus with maternal placenta (most mammals, some sharks).
  • Amniote: vertebrates with amnion-enclosed egg (reptiles, birds, mammals) enabling terrestrial reproduction.
  • Endotherm vs Ectotherm
    • Endotherm: generate metabolic heat; stable internal T (birds, mammals).
    • Ectotherm: rely on environment; behavioral thermoregulation (reptiles, amphibians, fish).

Parts of the Amniotic Egg & Functions

  • Amnion: fluid-filled membrane cushioning embryo.
  • Chorion: gas exchange; forms placenta in eutherians.
  • Yolk Sac: nutrient storage (lipids, proteins); circulatory connection.
  • Allantois: waste storage; later respiratory surface.
  • Albumen: ‘egg white’; water & protein reserve; antimicrobial.
  • Shell (calcareous or leathery): protection yet porous for gas exchange.