bio test 4

What does protometazoan mean?

Hypothetical common ancestor of all animals; a primitive organism that gave rise to the animal kingdom.

To which eukaryotic supergroup do animals belong

Opisthokonta

What other major groups are in Opisthokonta

Fungi and choanoflagellates

What characteristics make animals unique?

Multicellular, heterotrophic, no cell walls, most can move, use contractile proteins (actin/myosin), diploid-dominant, have specialized tissues.

Which moved onto land first – plants or animals?

Plants (~470 mya), then animals (~420 mya).

How do diploblasts differ from triploblasts?

Diploblasts have 2 germ layers (ectoderm, endoderm). Triploblasts have 3 (ectoderm, mesoderm, endoderm).

What does ectoderm develop into?

Skin and nervous system

What does mesoderm develop into?

Muscles, circulatory system, skeleton

What does endoderm develop into?

Digestive tract lining, respiratory tract, liver, pancreas.

Advantage of multicellularity?

Cell specialization, larger body size, greater complexity

Advantage of bilateral symmetry?

Enables directional movement and detection of stimuli from one end.

Advantage of cephalization?

Concentration of sensory organs and brain at the front for efficient navigation.

Advantage of triploblasty?

Mesoderm allows complex muscles, circulatory system, and organs to develop.

Advantage of segmentation?

Allows body region specialization; damage to one segment doesn't affect others.

Advantage of appendages

Enable locomotion, feeding, sensing, and reproduction.

Are all insects arthropods, or all arthropods insects?

All insects are arthropods, but not all arthropods are insects. Arthropoda also includes arachnids, crustaceans, and myriapods.

What are trilobites?

Extinct marine arthropods with segmented bodies and hard exoskeletons; early relatives of modern arthropods showing aquatic origins.

Evidence arthropods evolved from aquatic ancestors?

Trilobite fossils; crustaceans are basal and aquatic; gills are homologous to book lungs/tracheae; many insects have aquatic larval stages.

Advantage of the cuticle/exoskeleton for arthropods?

Prevents desiccation, provides structural support, and offers protection on land.

Do all arthropods breathe the same way?

No. Insects/myriapods use tracheae; spiders use book lungs; aquatic crustaceans use gills; some crustaceans use moist gill-like structures.

Two ways arthropods sense terrestrial environments?

1) Compound eyes for light/movement detection. 2) Antennae/setae (chemoreceptors/mechanoreceptors) for smell, touch, and vibration in air.

How have appendages made arthropods so successful?

Modified for walking, jumping, swimming, grasping, chewing, sensing, and reproduction — enormous functional versatility.

Key terrestrial adaptations of arthropods?

Waterproof cuticle, tracheal system/book lungs, jointed appendages, compound eyes/antennae, internal fertilization, uric acid excretion.

Key features of chordates?

Notochord (structural support) and dorsal hollow nerve cord (becomes brain/spinal cord).

Key features of vertebrates?

Vertebral column, cranium, endoskeleton.

Are all vertebrates chordates, or all chordates vertebrates?

All vertebrates are chordates, but not all chordates are vertebrates (e.g., lancelets and tunicates lack a backbone).

Key feature of Gnathostomes?

Jaws (evolved from gill arches), enabling active predation.

Key feature of Osteichthyes?

Bony endoskeleton

Difference between ray-finned and lobe-finned fish?

Ray-finned: fins supported by thin bony rays. Lobe-finned: fins supported by fleshy muscular lobes with bones homologous to limb bones.

Which fish group led to tetrapods?

Lobe-finned fish.

Which group includes mudskippers?

Ray-finned fish.

Which clades independently transitioned to land?

Arthropods, tetrapods (from lobe-finned fish), pulmonate gastropods (land snails), nematodes.

What does tetrapod mean?

"Tetra" = four, "pod" = foot/limb. Four-limbed vertebrates (or descended from them).

How do fossils show tetrapods evolved from lobe-finned fish?

Tiktaalik — transitional fossil with fins containing bones homologous to humerus, radius, and ulna; also had ribs and a neck.

First fully terrestrial group of tetrapods?

Reptiles (amniotes). Amphibians walked on land first but still needed water to reproduce.

Why was the amniotic egg a major innovation?

Membranes and shell protect embryo, prevent desiccation, allow gas exchange, and store nutrients — freeing amniotes from water for reproduction.

Key terrestrial adaptations of tetrapods?

Four limbs, lungs, amniotic egg, waterproof skin, internal fertilization, efficient kidneys.

What system creates hormones?

Endocrine system.

How do hormones travel through the body?

Released into the bloodstream; travel to target cells with specific receptors.

What do hormones do?

Regulate growth, metabolism, reproduction, water balance, and stress response by binding receptors and altering cell behavior.

How do lipid-derived and peptide hormones differ?

Lipid-derived: hydrophobic, bind intracellular receptors, directly affect gene expression, slower effect. Peptide: hydrophilic, bind surface receptors, trigger second messenger cascades, faster effect.

How can low hormone levels have large effects?

Signal amplification — one hormone triggers a cascade (e.g., cAMP → kinase) that activates thousands of enzymes.

How does ADH maintain homeostasis?

Released when blood osmolarity is high → increases water reabsorption in kidney collecting ducts → restores normal osmolarity → negative feedback stops ADH release.

Direct vs. indirect development?

Direct: born/hatched as miniature adults (e.g., reptiles). Indirect: larval stage that undergoes metamorphosis (e.g., frogs, butterflies).

Do animals have diploid or haploid dominant life cycles?

Diploid dominant. Gametes are the only haploid stage.

When is asexual reproduction favored?

Stable, favorable environments — fast reproduction, no mate needed, low energy cost.

When is sexual reproduction favored?

Variable or unpredictable environments — genetic diversity increases adaptability.

What is parthenogenesis? Example?

Reproduction without fertilization. Examples: hammerhead sharks, whiptail lizards.

What are nudibranchs' reproductive strategy?

Simultaneous hermaphrodites — both partners exchange sperm during mating.

What are oysters' reproductive strategy?

Sequential hermaphrodites — change sex over their lifetime.

What trade-off do animals and plants share in osmoregulation?

To exchange gases, surfaces must be moist/permeable, which also causes water loss — balancing gas exchange vs. desiccation.

Passive vs. active transport?

Passive: down concentration gradient, no ATP. Active: against gradient, requires ATP.

Which direction do molecules naturally move?

High to low concentration. Active transport is needed to move against the gradient (low to high).

What is an electrochemical gradient?

A gradient driven by both ion concentration differences AND electrical charge differences across a membrane.

How does a planarian acquire and distribute O₂?

Diffusion through skin; no circulatory system — diffusion alone (body is flat/thin).

How does an amphibian acquire and distribute O₂?

Through skin and simple lungs; closed circulatory system with 3-chambered heart.

How does a honeybee acquire and distribute O₂?

Spiracles → tracheal tubes directly to tissues; blood does not carry O₂.

How does a dog acquire and distribute O₂?

Lungs; closed circulatory system with 4-chambered heart; hemoglobin carries O₂ in blood.

Which excretory structure goes with which group?

Flame cells → planarians. Malpighian tubules → arthropods. Kidneys → mammals.

How does the excretory system maintain homeostasis?

Removes nitrogenous wastes, regulates ion concentrations, controls water balance by selectively reabsorbing or excreting water and ions.

How do amphibians osmoregulate?

Absorb water through pelvic patch; produce dilute urine in freshwater; reabsorb water from bladder when dry; mucus slows evaporation; some aestivate.

How did mammals adapt for reproduction?

Placenta nourishes embryo in uterus (stable environment, longer development). Mammary glands provide milk with nutrients and antibodies after birth.

Prokaryotes vs. eukaryotes — key differences?

Prokaryotes: no nucleus, no membrane-bound organelles, circular DNA, smaller (Bacteria/Archaea). Eukaryotes: nucleus, membrane-bound organelles, linear DNA, larger (animals, plants, fungi, protists).