🌱BIO153 Animals

Eumetazoa

non-sponge animals that have “true tissue” such as muscles and nerves

What type of symmetry does the basal group of Eumetazoa have?

radial symmetry

What is animalia also known as?

Metazoa

What are the closest living relatives to animals?

Choanoflagellates, a type of unicellular protist

How are choanoflagellates used to determine the origin of multicellular organisms?

they have proteins that stick onto other cells, forming a colony

What were the first group of animals to diverge from the rest of animalia?

Porifera (sponges)

What are the three major clades of Bilateria?

Lophotrochozoa, Ecdysozoa, Deuterostomia

Radial symmetry

body can be divided into two equal halves by any plane passing through the center

eg. jellyfish, sea stars, corals, sea anemones

Bilateral symmetry

body can be divided symmetrically into a “left side” and “right side”

eg. humans, fish, birds, insects

What are three specific traits that vertebrates have?

backbone, hinged jaws, limbs with digits

How does a zygote divide?

by cleavage

Cleavage (division)

mitotic cell division not accompanied by cell growth

What does the zygote form after multiple cleavages?

a blastula

Blastula

a single layer of cell covering a hollow space

Blastocoel

the hollow space inside the blastula

Gastrulation

one end of the blastula’s surface internalizes, allowing the blastula to become a gastrula

What does gastrulation lead to?

the beginning of cell differentiation, where different cell layers develop into different tissues and organs

What two surfaces is the gastrula composed of?

Archenteron and Blastopore

Archenteron

cavity inside the gastrula

Blastopore

opening into the cavity where both the mouth and anus form

Deuterostomes

organisms that form the anus before the mouth in embryonic development

Ecto-

outside

Endo-

inside

Ectoderm

cell layer that forms skin, hair, teeth, nervous system, germ cells, etc.

Endoderm

cell layer that forms epithelial surfaces of digestive, respiratory, excretory and reproductive tracts, etc.

Mesoderm

cell layer that forms skeleton, muscle, circulatory system, etc. (not all animals have this)

Incomplete Metamorphosis

gradual growth of larva into adult via multiple molts (nymphs)

Complete Metamorphosis

 growth of larvae into adult via a pupal stage

What are the two main classes of deuterostomes?

Echinoderms and Chordates

Echinoderms

invertebrates such as sea stars, sea urchins

Chordates

vertebrates such as fish, reptiles, mammals, (and some invertebrates)

What are the four major derived traits of chordates?

Notochord, hollow nerve cord, pharyngeal slits, post-anal tail

NNGT (notochord, nerve cord, gills, tail)

Notochord

A flexible rod found between the digestive tube and nerve cord. In vertebrates, the backbone develops around the embryotic notochord.

Dorsal hollow nerve cord

The nerve cord that develops from the neural plate in the ectoderm into a neural tube.

What does the neural tube form in vertebrates?

the spinal cord

Pharyngeal slits

Pharyngeal clefts that develop into pharyngeal gills in some chordates. In humans, pharyngeal clefts differentiate into other tissues in utero

What is distinctive about early diverged vertebrates such as lampreys?

They lack jaws and have a cartilage skeleton. The cartilage skeleton can be mineralized with calcium for added support.

What is special about lancelets?

they have all the features of a chordate, however they do not have a backbone.

What qualifies some invertebrates to be members of Chordata?

they have all four derived traits of Chordata at some stage in their life, even if they usually disappear by adulthood.

Ray-finned fishes

Fins are made of bony rays connected with webs without muscular structure

Lobe-finned fish

Pectoral and pelvic fins have a thick muscle supporting the bony fin, usually seen in extinct species or living fossils such as coelacanths.

Tetrapods

Gnathostomes that have limbs with digits, a four-footed animal

Amniotes

Tetrapods with terrestrially adapted eggs

Amnion

encloses the amniotic fluid that the embryo floats in

Ectothermic

“cold-blooded”

Endothermic

“warm blooded,” less energy efficient than ectothermic but able to withstand harsh conditions

What covers the archenteron?

the endoderm and then the ectoderm

Where does the mesoderm form in gastrulation?

between the ectoderm and endoderm

Monozygotic twins

occur when a egg fertilized by a single sperm is split into two

Dizygotic twins

occur when two eggs are fertilized simultaneously by two different sperm

What is the sponge body made up of?

two cell layers filled in by mesohyl (“middle matter”) that provides good access to water, hence the lack of need for a circulatory system

What does a sedentary suspension feeder do?

they draw in water from their side-pores and out from the central cavity, filtering out food particles suspended in water

Choanoflagellate cells look very similar to what?

the collar cells of sponges

Lophophore

crown of ciliated tentacles for feeding

Trochophore

larval form of the group of invertebrates Lophotrochozoa

Where does the clade Ecdysozoa get its name from?

from “ecdysis,” the molting of the exoskeleton that a lot of organisms partake in

What does the visceral mass in mollusks do?

it contains most of the inner organs

What does the mantle in mollusks do?

covers the visceral mass and secretes the shell

the mantle may extend beyond the visceral mass to create mantle cavity

What does the mantle cavity in mollusks contain?

the gills, anus, excretory organs, etc.

What is the difference between the mantle in cephalopods and in mollusks?

the mantle in on the outside and the shell is minimized or lost in cephalopods

Siphon

an organ found in cephalopods and mollusks that expels water

Which group of animals contains more species than any other eukaryote?

Ecdysozoans

What composes the segmented body of insects?

head, thorax (“torso” where legs are), post-genital region

What happens to the notochord in humans?

the embryotic notochord reduces and becomes part of the intervertebral disc in the spinal column

What happens to the nerve cord in humans?

it develops into the spinal cord

What are tunicates and what are they closely related to?

An invertebrate animal whose larvae present all four Chordate traits. They are more closely related to vertebrates than lancelets.

Gnathostomes

jawed vertebrates, includes cartilage-skeleton fish such as sharks and rays

What is the sister group to tetrapods?

Lung fish that adapted to life on land, with the fins evolving into limbs with digits.

What is another term for placental mammals?

Eutherians

How are carnivore stomachs adapted to their diets?

they have large, expandable stomachs since they go long intervals between feeding and need to eat large quantities when they can

How are herbivore and omnivore stomachs adapted to their diets?

they have longer digestive tracts since vegetation is harder to digest

Why is beneficial gut bacteria important for herbivores?

the bacteria can break down cellulose walls in vegetation that are otherwise unable to be digested

What group of primates were the first to diverge from the common ancestor?

The clade that includes lemurs, lorises, bush babies, and tarsiers

Anthropoids

all primates including monkeys, apes, and humans

Hominins

extinct species more closely related to humans than other apes