LAB 2 Flashcards
Animal Phylogeny
What does ‘caudal’ refer to in anatomy?
The tail region of an animal
What is the definition of ‘posterior’?
The tail or hind end of an animal
Define ‘anterior’.
The front or head end of an animal
What does ‘cephalic’ mean?
The head region, specifically
What is meant by ‘ventral’?
The underside of an animal
What does ‘dorsal’ refer to?
The back or uppermost of an animal
What does ‘distal’ mean in anatomical terms?
Structure farthest away from a point of reference
Define ‘proximal’.
Structure nearest to a point of reference
What does ‘oral’ refer to?
Mouth region
What is the current understanding of animal classification?
Animals are monophyletic and belong to a single clade, the Metazoa
What does the phylum ‘Porifera’ consist of?
Sponges
What organisms are included in the phylum ‘Cnidaria’?
Corals, anemones, jellies
Name the organisms classified under the phylum ‘Echinodermata’.
Sea stars, sea cucumbers, sea urchins
What is included in the phylum ‘Chordata’?
Fish, amphibians, reptiles (including birds), mammals
What type of organisms are found in the phylum ‘Platyhelminthes’?
Flat worms
What are examples of organisms in the phylum ‘Annelida’?
Segmented worms
What does the phylum ‘Mollusca’ include?
Chitons, slugs, snails, clams, squid, octopi
What does the phylum ‘Brachiopoda’ consist of?
Lampshells
What are organisms in the phylum ‘Nematoda’ commonly known as?
Round worms
What does the phylum ‘Arthropoda’ include?
Spiders, centipedes, crustaceans, insects
What is the first stage of animal development after fertilization?
Cleavage
What occurs during the cleavage stage?
A series of rapid cell cycles with short to no G1 or G2 phases
What is the result of cleavage?
A solid ball of cells known as the morula, which hollows out to become a blastula
What is the blastula?
A hollow ball that is typically one cell layer thick
Define ‘gastrulation’.
The process where the one-layered embryo folds in to produce a multiple layered embryo—the gastrula
What is the archenteron?
The beginnings of the digestive tract in the gastrula
What is the significance of the blastopore?
It is the first opening that develops into the digestive tract
True or False: Sponges have a protein layer that isolates their cells.
False
What is the evolutionary significance of radial symmetry?
There are numerous ways to cut them in half
What characterizes bilateral symmetry?
There is only a single plane of symmetry
What is ‘cephalization’?
The evolution of the head
What group do cnidarians belong to?
The Radiata
True or False: The Radiata is a monophyletic group.
False
In what forms can Obelia be found?
In polyp form (hydroid stage) and as adult free-swimming medusa
What surrounds the mouth in the hydroid stage of Obelia?
Tentacles
In the medusa stage of Obelia, where does the mouth extend from?
Centrally located stomach
What is the body form of Hydra?
Polyp body form
What type of symmetry do radially symmetrical cnidarians exhibit?
Multiple planes of symmetry
What is the single body axis of radially symmetrical organisms called?
Oral-aboral axis
In animals with bilateral symmetry, what separates their right and left halves?
Cutting these animals in half
What are the dorsal and ventral sides of an animal with bilateral symmetry?
Dorsal: back, Ventral: belly
What are the two major tissue layers found in Eumetazoan embryos?
Ectoderm and endoderm
What term describes animals with only two tissue layers?
Diploblastic
What term describes animals with three tissue layers?
Triploblastic
What is the process called that leads to the development of distinct tissue layers in embryos?
Gastrulation
What is formed during gastrulation that becomes the opening to the digestive tract?
Blastopore
What are animals whose blastopore becomes the mouth called?
Protostomes
What are animals whose blastopore becomes the anus called?
Deuterostomes
What does the term ‘deuterostome’ literally translate to?
Second mouth
Which two phyla are included in the clade Deuterostomia?
- Echinodermata
- Chordata
What is the basal taxon of chordates?
Cephalochordata
What is a notable feature of the amphioxus?
Large notochord
What is located dorsal to the notochord in amphioxus?
Dorsal hollow nerve cord
What type of gut does amphioxus have?
Simple gut from mouth to anus
Fill in the blank: The two types of animals with true tissues are _______ and _______.
Diploblastic, Triploblastic
True or False: All diploblastic animals have two openings to their digestive tract.
False
What are the three clades into which chordate representatives are divided?
- Cephalochordata
- Urochordata
- Vertebrata
How do amphioxus primarily perform gas exchange?
Through thin skin and pharyngeal gill slits
Pharyngeal gill slits assist in creating a water current for suspension feeding.
Which group of organisms is more closely related to vertebrates than cephalochordates?
Urochordates
This relationship is based on molecular evidence.
What are tunicates commonly known as?
Sea squirts
They are named for the thin covering (tunic) over their body.
What key chordate features are present in the larval stages of urochordates?
Gill slits, post anal tail, notochord, dorsal hollow nerve cord
The rudimentary brain and sensory organs are also located in the head.
What happens to the notochord and dorsal hollow nerve cord in adult urochordates?
They are absent; only a simple nerve ganglion is present.
What are the three major clades within Bilateria?
Deuterostomia, Lophotrochozoa, Ecdysozoa
These clades are established based primarily on molecular homologies.
How do members of the Lophotrochozoa grow?
Continuously
This contrasts with the Ecdysozoa, which grow by spurts.
List some phyla included in the Lophotrochozoa clade.
- Platyhelminthes
- Brachiopoda
- Annelida
- Mollusca
- 14 other phyla
It is a vast and diverse group of animals.
What ciliated feeding structure do some Lophotrochozoa, like brachiopods, possess?
Lophophore
What is the ciliated larval stage called that annelids and molluscs go through?
Trochophore
What common feature do all members of the Lophotrochozoa exhibit?
Continuous growth
Juveniles gradually get larger until reaching adult size.
How do Ecdysozoans grow?
By shedding a hardened covering or cuticle (moult) and growing rapidly before creating a new one.
True or False: All deuterostomes grow continuously.
True
What distinguishes growth patterns between the two protostome clades?
Continuous growth in Lophotrochozoa vs. spurts in Ecdysozoa.
