animal diversity

Animals

Multicellular eukaryotes, heterotrophs, capable of movement, share common ancestry.

Symmetry

Body plan of an animal; can be bilateral (two sides) or radial (around one axis).

Blastula

Early embryonic stage; a hollow ball of cells.

Blastopore

Opening on early embryo that becomes the mouth or anus.

Protostomes

Blastopore develops into the mouth.

Deuterostomes

Blastopore develops into the anus.

Germ Layers

Groups of embryonic cells that develop into different tissues and organs.

Diploblastic

Animals with two germ layers (ectoderm and endoderm); cannot have a circulatory system.

Triploblastic

Animals with three germ layers (ectoderm, mesoderm, endoderm).

Ectoderm

Outermost layer; forms dermal and neural tissues.

Endoderm

Innermost layer; forms gut lining.

Mesoderm

Middle layer; forms connective tissues like muscles and blood.

Animal Classification

Based on presence of tissues, symmetry type, protostome/deuterostome, and molting.

Phylum Porifera

Sponges; asymmetric, mostly marine, lack tissues and organs, collar cells filter food.

Phylum Cnidaria

Jellyfish, coral, anemones; radial symmetry, tissues present, gastrovascular cavity, two body forms (polyp, medusa), stinging cells (cnidocytes).

Phylum Platyhelminthes

Flatworms; no circulatory system, gastrovascular cavity if present, tapeworms lack digestive tract.

Phylum Annelida

Segmented worms; mouth and anus, closed circulatory system, no respiratory system.

Phylum Nematoda

Roundworms; no segments, no circulatory or respiratory systems, complete digestive tract, shed cuticle.

Phylum Mollusca

Protostomes, most have shells, open circulatory system (except cephalopods).

Gastropoda

Snails, slugs; some lack shells.

Cephalopoda

Squid, octopus; mobile, closed circulatory system, well-developed nervous system.

Phylum Arthropoda

Insects, crustaceans, spiders; segmented body, exoskeleton of chitin, molt, open circulatory system, metamorphosis (larva → pupa → adult).

Phylum Echinodermata

Sea stars, sea urchins; radial adults, bilateral larvae, water vascular system for locomotion, feeding, and gas exchange, calcium carbonate internal skeleton.

Phylum Chordata

Notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail; three subphyla: Urochordata, Cephalochordata, Vertebrata.

Subphylum Vertebrata

Vertebrae protect nerve cord; includes fish, amphibians, reptiles, birds, mammals.

Fish

Jawless or jawed, fins, swim bladder for buoyancy (homologous to lungs).

Amphibia

Tetrapods; lungs and skin for breathing, eggs require moisture.

Amniotes

Fertilization inside female, amniotic egg, adaptations (skin, excretory system) to prevent water loss.

Class Reptilia

Lizards, snakes, turtles, crocodiles; tails present, ectothermic.

Birds

Flight adaptations, hollow bones, feathers, endothermic.

Class Mammalia

Hair, mammary glands, young develop in uterus, endothermic.

Homeostasis

Maintaining stable internal conditions despite changing external conditions.

Negative Feedback

Resists change to maintain homeostasis (e.g., shivering).

Positive Feedback

Enhances change, moving system away from homeostasis (e.g., pregnancy).

Circulatory System

Moves gases, nutrients, and waste throughout the body; essential for larger organisms.

Arteries

Carry blood away from the heart; higher pressure.

Veins

Carry blood toward the heart; lower pressure.

Capillaries

Thin vessels where exchange of gases, nutrients, and wastes occurs.

Sphincters

Muscles controlling blood flow through capillary beds.

Closed Circulatory System

Blood contained in vessels; found in vertebrates, annelids, cephalopods.

Open Circulatory System

Blood partially contained; mixes with extracellular fluid; found in arthropods and most mollusks.

Pulmonary Circuit

Moves blood to/from lungs or gills.

Systemic Circuit

Moves blood to/from the rest of the body.

Atrium

Upper chamber receiving blood from veins.

Ventricle

Lower chamber pumping blood to body or lungs.

Diastole

Heart relaxes and fills with blood.

Systole

Heart contracts, pushing blood into arteries.

SA Node

Initiates atrial contraction.

AV Node

Delays signal to allow ventricles to fill before contracting.

Coronary Arteries

Deliver oxygen and nutrients to heart muscle; blockages cause heart attacks.

Protostome vs Deuterostome

Determined first by symmetry.

Important thing to remember about Cnidarians, Porifera

neither protostomes or deuterostomes (no symmetry)

Indirect Development

Larval and adult forms look different; helps species survival since adult and larval forms occupy different niches

Blood Pressure

Arteries have higher pressure than veins due to proximity to heart.

Lobe-finned Fish

Fins with bones and joints; link to land vertebrates (tetrapods).

Directional Selection

Favors one extreme phenotype, causing the population’s average trait to shift in that direction over time.

Stabilizing Selection

Favors intermediate phenotypes and selects against extreme traits, keeping the average stable.

Disruptive Selection

Favors both extreme phenotypes while selecting against intermediate ones, potentially splitting the population.

Balancing Selection

Maintains multiple phenotypes in a population by favoring genetic diversity (e.g., heterozygote advantage or frequency