Bio II Chapter 27

filter feeders

animal that feeds by using a filtration mechanism to strain small organisms or food particles from its surroundings.

basal members of a taxonomic group

taxon whose evolutionary lineage diverged early in the history of the group.

derived members of a taxonomic group

possess shared, unique traits that distinguish them from other members of a larger group

Ediacaran biota

early group of macroscopic, soft-bodied, multicellular eukaryotes known from fossils that range in age from 635 million to 541 million years old.

choanocytes

flagellate feeding cells found in sponges; also called collar cells (named for the finger-like projections that form a “collar” around the flagellum)

amoebocytes

cells that use pseudopodia for movement; found in most animals, various uses that varies between animals (also found in sponges)

Cnidarian life forms/cycle

planula (free moving ciliated larva) → polyp (immobile form that attaches to substrate; reproduce sexually or asexually to form new polyps or medusa) → medusa (free moving, reproduce sexually by releasing gametes forming planula)

gastrovascular cavity

a fundamental feature of Cnidarians, serving both digestive and circulatory functions; single opening acting as both the mouth and anus

Cambrian Explosion

when many present-day phyla of animals first appeared in the fossil record. This burst of evolutionary change occurred about 535–525 million years ago and saw the emergence of the first large, hard-bodied animals

radial symmetry

body has wheel like form that can be divided infinitely many ways into two similar halves (typical organism is stuck to substrate → Cnidarians)

Asymmetric

no central axis in which organism can be divided into two equal parts (Porifera → sponges)

Bilateral Symmetry

one central axis/one way to cut into two similar parts (Bilateria → squirrels)

pentaradial symmetry

an exception to Bilateria applied to starfish (5 axis in which body can be cut into two similar parts); starfish larvae/babies have bilateral symmetry

dorsal/ventral

back or posterior side of body / front or anterior side

anterior/posterior

front / back

germ layers

ectoderm, endoderm, mesoderm

gastrula

stage in embryonic development, single layered structure → multilayered

ectoderm

cells on the outside of gastrula become body covering (leads to skin, nervous system, eyes)

mesoderm

middle layer of cells form the muscle and organs (leads to bones, muscles, circulatory and reproductive systems)

ectoderm

cells on the inside of gastrula that become lining of the gut (leads to digestive and respiratory systems)

Bag/incomplete digestive system

no anus; food goes in and waste comes out of the mouth (hydra, jellyfish of phylum Cnidaria)

Tube-within-a tube/complete digestive system

mouth and anus are at opposite ends of tract/tube (earthworms of phylum Annelida)

diploblasts

have two germ layers (no mesoderm); includes Cnidaria

triploblasts

have all three germ layers; include all Bilateri: Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata, and Chordata

acoelomate

lacks true body cavity between the tissue layers (no cavity); includes Cnidaria and Platyhelminthes

pseudocoelomate

has body cavity called pseudocoelom, fluid filled cavity between gut and out body wall, not completely lined by mesoderm (yes, but no true cavity); includes Nematoda

coelomate

has true body cavity and coelom, fluid filled spaces lined with mesoderm; separates digestive tract from outer body wall, contained internal organs; includes all bilaterias (Annelida, Mollusca, Arthropoda, Enchinodermata, Chordata) except Nematoda and Platyhelminthes

protostomes

the first opening in the embryo becomes the mouth; “proto” means first; mostly invertebrates (example: leech, bees, etc.)

deuterostomes

the first opening in the embryo becomes the anus, and the mouth develops later: '“deutero” means second; includes both invertebrates and vertebrates (example: Humans/mammals)

Cephalization

concentration of nervous/sensory tissue and structures concentrated near head

Chordates

Bilateral, cephalization, complete digestive system, triploblast, coelomate;

Possess notochord, pharyngeal slits or clefts (gills → found in humans during embryonic development), post-anal tail

Notochord

semi-flexible dorsal nerve cord, replaced by the vertebral column in vertebrates

agnathostomes

jawless fish, include lampreys and hagfishes

gnathostomes

are jawed vertebrates, encompassing all jawed fish and tetrapods (animals with four limbs) like mammals, birds, reptiles, and amphibians

chondrichthyans

vertebrates with skeletons mostly made of cartilage, often imbued with calcium; includes sharks and rays

osteichthyans

member of vertebrate clade with jaws and mostly bony skeletons, have lungs or lung derivatives; diversified into two lineages, ray-finned fishes and the lobe-fins

tetrapods

vertebrates characterized by limbs with digits; includes mammals, amphibians, birds, and some reptiles

arthropod

invertebrate animals like spiders, insects, crustacean; exoskeleton is made of sclerotin (a protein) & chitin (a polysaccharide)

Tiktaalik

very recent discovery of species, had fins, gills, and lungs, and its body was covered in scales; unlike a fish, Tiktaalik had a full set of ribs that would have helped it breathe air and support its body. Also unlike a fish, had a neck, allowing it to move its head about

amniotes

a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals, characterized by having an amniotic egg with amnion, chorion, yolk sac, allantois membranes; fertilized egg within the mother

amnion

inner membrane fluid-filled sac, amniotic sac, surrounds and protects the fetus during development. Adaptation that prevents them from drying out allowing the species to no longer rely on water (move away from water to fully on land)

synapsids

member of amniote clade, distinguished by a single hole on each side of the skull (eye sockets); the only lineage surviving is mammals; gave rise to three clades of mammals: monotremes, marsupials, eutherians

monotremes

platypus → mammal that has eggs; part of mammalian phylogenetic tree

marsupials

give birth very early, development continues within pouch; can abort fetus if conditions get too hard

eutherians

placental mammalian; young completes embryonic development within mother’s uterus, joined to mother via the placenta

placenta

a structure in which nutrients diffuse into the embryo from the mother's blood

hominins

group consisting of humans and the extinct species that are more closely related us than to chimps

suspension feeders

organisms that remove food particles suspended in water; use various mechanisms, like cilia, tentacles, or filters to separate particles from water

Porifera (phylum)

Asymmetric, no cephalization, no digestive cavity (intracellular digestion), no germ layers (Example→sponges) (Metazoa clade)

Cnidaria (phylum)

radial symmetry, no cephalization, incomplete digestive system (only one opening where food and waste enters/exits), diploblast (lack mesoderm), acoelomates), have stinging cells called cnidocytes (Example→polyps, medusa, planula body forms, zooxanthellae→photosynthesizing dinoflagellates) (Eumetazoa clade)

Platyhelminthes (phylum)

bilateral, cephalization, incomplete digestive system (exception to Bilateria), triploblast, acoelomates, have well developed organ systems in free living species (Examples→tapeworms, flukes) (Bilateria clade)

Nematoda (phylum)

bilateral, cephalization, complete digestive system, triploblast, pseudocoelomates, no circulatory or respiratory systems (Examples→hookworms, pinworms, ascarid) (Bilateria clade)

Annelida (phylum)

bilateral, cephalization, complete digestive system, triploblast, coelomates, Metamerism: body segments divided by septa have same sets of organs; no respiratory system (Examples→segmented worms, earthworms, leech) (Bilateria clade)

Mollusca (phylum)

bilateral, cephalization, complete digestive system, triploblast, coelomates, Respiratory system located on mantle, most groups possess a tooth like radula (Examples→snails,, slugs, octopus, squid, chitons) (Bilateria clade)

(phylum)

bilateral, cephalization, complete digestive system, triploblast, coelomates, jointed appendages cuticle reinforced with polysaccharides called Chitins (most rich phylum of animals), largest of all animal phyla (Examples→arachnids, crustaceans, centipedes, millipedes, insects) (Bilateria clade)

Echinodermata

bilateral, cephalization, complete digestive system, triploblast, coelomates, water vascular system that uses water pressure for locomotion (Examples→sea stars, brittle stars, feather stars, sand dollars, sea urchins, sea cucumbers)

Chordata

bilateral, cephalization, complete digestive system, triploblast, coelomates, possess a semi-flexible dorsal nerve cord called notochord replaced by vertebral column in vertebrates (Examples→1/2 of chordata are bony fish; vertebrates, humans, amphibians, reptiles) (Bilateria clade)

Metazoa

all animals; multicellularity (derived trait); most recent common ancestry for all animals

Eumetazoa

TRUE animals; animals with true tissue (everything but sponges); most recent common ancestor for all true animals