Exam 3

Question 1

archenteron

Answer 1

The archenteron is the primitive gut formed during early embryonic development. It develops during gastrulation and will eventually give rise to the digestive system.

Question 2

bilateral symmetry

Answer 2

Bilateral symmetry is a body plan in which an organism can be divided into two equal halves along a single plane, with mirror-image right and left sides. Examples include humans and most animals.

Question 3

blastopore

Answer 3

The opening that forms during early embryonic development at the site of the invagination of cells during gastrulation. It eventually develops into either the mouth or the anus

Question 4

blastula

Answer 4

A blastula is an early-stage embryo that forms after the zygote undergoes several rounds of cell division (cleavage). It consists of a hollow ball of cells, with an inner fluid-filled cavity called the blastocoel. The blastula stage precedes gastrulation, during which the layers of the embryo start to differentiate.

Question 5

body plan

Answer 5

A body plan refers to the general structure and organization of an organism’s body, including the arrangement of its tissues, organs, and body cavities. It dictates the overall shape, symmetry, and developmental pattern of the organism. Examples include bilateral symmetry, radial symmetry, and asymmetry.

Question 6

Budding

Answer 6

A form of asexual reproduction where a new organism grows from a small outgrowth (bud) of the parent organism.

Question 7

cephalothorax

Answer 7

A body region found in some arthropods (like spiders and crustaceans) that combines the head and thorax into one fused segment.

Question 8

Chelicera

Answer 8

Pair of appendages in arachnids (spiders, scorpions) that serve as mouthparts for grasping or piercing food.

Question 9

Choanocyte

Answer 9

A type of cell found in sponges, responsible for creating water currents and filtering food particles from the water.

Question 10

Cleavage

Answer 10

The series of rapid cell divisions that occur immediately after fertilization, leading to the formation of a blastula.

Question 11

Coelom

Answer 11

A fluid-filled body cavity located between the digestive tract and the body wall, present in most multicellular animals, allowing space for internal organs.

Question 12

Determinate cleavage

Answer 12

A type of cleavage in which the fate of the cells is determined early in development, characteristic of protostomes

Question 13

Deuterostome

Answer 13

A group of animals (e.g., chordates and echinoderms) in which the blastopore develops into the anus and the mouth forms later.

Question 14

Diploblast

Answer 14

An organism that develops from two primary germ layers: the ectoderm and endoderm (e.g., cnidarians like jellyfish).

Question 15

Ectoderm

Answer 15

The outermost of the three primary germ layers in the embryo, giving rise to the skin, nervous system, and sensory organs.

Question 16

Endoderm

Answer 16

The innermost of the three primary germ layers, which develops into the digestive and respiratory systems.

Question 17

Endoskeleton

Answer 17

A skeleton located inside the body, made of bone or cartilage (e.g., vertebrates).

Question 18

Exoskeleton

Answer 18

A rigid external covering that supports and protects the body, typical in arthropods and some other invertebrates.

Question 19

Gastrula

Answer 19

The stage in embryonic development after the blastula, characterized by the formation of three germ layers (ectoderm, mesoderm, and endoderm).

Question 20

Hemocoel

Answer 20

A body cavity found in some invertebrates (like arthropods), filled with hemolymph (a fluid analogous to blood).

Question 21

Hermaphrodite

Answer 21

An organism that has both male and female reproductive organs, allowing it to produce both eggs and sperm.

Question 22

Indeterminate cleavage

Answer 22

A type of cleavage where the fate of each cell is not determined early in development, characteristic of deuterostomes. Cells can still form complete organisms if separated.

Question 23

Mantle

Answer 23

A soft, protective outer layer in mollusks that secretes the shell (in species with shells) and can also function in respiration and movement.

Question 24

Medusa

Answer 24

The free-swimming, bell-shaped body form of cnidarians like jellyfish. It is one of the two primary body forms, the other being the polyp.

Question 25

Mesoderm

Answer 25

The middle germ layer in the embryo, which gives rise to muscles, the circulatory system, bones, and other structures.

Question 26

Nematocyst

Answer 26

A specialized cell in cnidarians (like jellyfish and corals) containing a venomous stinger, used for defense or capturing prey.

Question 27

Parapodium

Answer 27

A paired, fleshy appendage found on some annelids (e.g., polychaetes), used for locomotion and respiration.

Question 28

Parthenogenesis

Answer 28

A form of asexual reproduction where offspring develop from an unfertilized egg, common in some insects, reptiles, and amphibians.

Question 29

Polyp

Answer 29

A sessile (non-motile) body form of cnidarians, typically cylindrical and attached to a surface (e.g., corals and sea anemones).

Question 30

Protostome

Answer 30

A group of animals in which the blastopore develops into the mouth first, and the anus forms later. Examples include arthropods and mollusks.

Question 31

Radial cleavage

Answer 31

A type of embryonic cleavage where the cells divide symmetrically around the axis of the embryo, typical of deuterostomes.

Question 32

Radial symmetry

Answer 32

A body plan in which body parts are arranged around a central axis, so the organism can be divided into similar halves along multiple planes (e.g., starfish, jellyfish).

Question 33

Radula

Answer 33

A specialized feeding organ found in many mollusks (e.g., snails), consisting of rows of teeth used to scrape or cut food.

Question 34

Spicule

Answer 34

A small, spike-like structure made of calcium carbonate or silica found in the skeletons of sponges and some other invertebrates.

Question 35

Spiral cleavage

Answer 35

A type of cleavage in which the cells divide at an angle to each other, characteristic of protostomes.

Question 36

Triploblast

Answer 36

An organism that develops from three primary germ layers: ectoderm, mesoderm, and endoderm. Most animals are triploblastic.

Question 37

Test

Answer 37

A hard, protective shell or covering, especially in some protists (e.g., foraminiferans) and echinoderms (e.g., sea urchins).

Question 38

Amniote

Answer 38

Vertebrates (including reptiles, birds, and mammals) that produce eggs with a protective amniotic membrane, or in the case of mammals, have internal development.

Question 39

Notochord

Answer 39

A flexible, rod-shaped structure found in the embryos of all chordates, providing support and serving as a precursor to the vertebral column in vertebrates.

Question 40

Swim bladder

Answer 40

An internal gas-filled organ found in many fish, used to control buoyancy and maintain a stable position in the water.

Question 41

Tetrapod

Answer 41

Vertebrates that have four limbs (e.g., amphibians, reptiles, birds, and mammals), a key evolutionary adaptation for life on land.

Question 42

Theropod

Answer 42

A group of bipedal dinosaurs, many of which were carnivorous, including the ancestors of modern birds (e.g., Tyrannosaurus rex).

Question 43

List the 4 features that characterize Animal kingdom

Answer 43

Multicellularity: Animals are made up of multiple cells that form complex structures and systems.
Heterotrophy: Animals are heterotrophs, meaning they obtain their food by ingesting other organisms.
Eukaryotic Cells: Animals have eukaryotic cells, meaning their cells contain a nucleus and other membrane-bound organelles.
Movement: Most animals are capable of some form of movement at some point in their life cycle (though some may be sessile as adults, like sponges).

Question 44

Describe the evolutionary relationship between protists and animals. Which group of protists are animals most closely related to?

Answer 44

Protists are considered the closest evolutionary relatives of animals. The evolutionary relationship is based on molecular evidence, particularly in the genetic similarities between certain protists and animals.
Animals are most closely related to a group of protists known as choanoflagellates, which are single-celled organisms that resemble the collar cells (choanocytes) of sponges. These cells have similar structure and function, suggesting that animals evolved from a common ancestor with choanoflagellates.

Question 45

Asexual and sexual reproduction and basic embryonic development in animals

Answer 45

Asexual Reproduction: Some animals reproduce asexually via processes like budding, fragmentation, or fission, where offspring are genetically identical to the parent.
Sexual Reproduction: Most animals reproduce sexually, involving the fusion of male and female gametes (sperm and egg), leading to the formation of a zygote.
Embryonic Development: In animals, early development typically includes cleavage (cell division), the formation of a blastula, and the subsequent development of germ layers (ectoderm, mesoderm, endoderm), followed by gastrulation.

Question 46

The role that larvae play in animal development

Answer 46

Larvae are often an early stage in the life cycle of animals. They typically have a different form from the adult and may have different feeding habits or modes of locomotion. The larval stage allows for dispersal and minimizing competition between young and adult individuals. For example, the larval form of a butterfly (caterpillar) is specialized for feeding, while the adult butterfly is specialized for reproduction.

Question 47

Explain the differences in animal body plans that support basic animal classification
Types of symmetry and the lifestyles associated with them
Tissues
Body cavity

Answer 47

Symmetry: Body symmetry (bilateral or radial) influences movement and lifestyle.
Tissue Organization: Presence or absence of tissue layers (e.g., diploblast vs. triploblast).
Body Cavity: The type of body cavity (coelom, pseudocoelom, or acoelomate) influences the internal organization and complexity.
Embryonic Development: Differences in blastopore fate (protostome vs. deuterostome) influence early development.
Radial Symmetry: Organisms can be divided into similar halves along multiple planes (e.g., starfish, jellyfish). This symmetry is suited for a sessile or slow-moving lifestyle.
Bilateral Symmetry: Organisms can be divided into two equal halves along one plane (e.g., humans, insects). This symmetry supports directional movement and is typically seen in active, mobile organisms.
Animals have specialized tissues that perform specific functions. Most animals are triploblastic, meaning they have three germ layers: ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer). The mesoderm gives rise to muscles, circulatory systems, and bones, while the ectoderm and endoderm form the skin, nervous system, and digestive organs.
Coelom: A body cavity fully lined with mesoderm (e.g., humans, earthworms). It allows for the development of complex organs and provides space for internal organs.
Pseudocoelom: A body cavity that is not fully lined by mesoderm (e.g., roundworms).
Acoelomate: Animals without a body cavity (e.g., flatworms).

Question 48

Contrast the embryonic development of protostomes and deuterostomes

Answer 48

Protostomes:
The blastopore becomes the mouth.
Spiral cleavage (cells divide in a spiral pattern).
Determinate cleavage (fate of cells is fixed early).
Deuterostomes:
The blastopore becomes the anus.
Radial cleavage (cells divide symmetrically).
Indeterminate cleavage (fate of cells is not fixed early, allowing for developmental flexibility).

Question 49

Describe key features of Porifera, Cnidaria, Platyhelminthes (and classes), Nematoda, Mollusca (and classes), Arthropoda (and particularly insects), Annelida (and classes), Echinodermata (and some classes), and Chordata (and subphlya). Know examples (e.g. jellyfish - Cnidaria, Planaria - Platyhelminthes)

Answer 49

Porifera (Sponges): Simple, porous body structure; lack true tissues; filter feeders. Examples: Sponges.
Cnidaria (Jellyfish, Corals, Anemones): Radial symmetry; cnidocytes with nematocysts (stinging cells); two body forms (polyp and medusa). Examples: Jellyfish, Corals, Sea anemones.
Platyhelminthes (Flatworms): Bilateral symmetry; no coelom; some are parasitic. Examples: Planaria, Tapeworms, Flukes.
Classes: Turbellaria (free-living), Cestoda (tapeworms), Trematoda (flukes).
Nematoda (Roundworms): Pseudocoelomates; complete digestive tract; many are parasitic. Example: Ascaris, Pinworms.
Mollusca (Mollusks): Bilateral symmetry; coelomates; often have a shell and a mantle. Classes: Gastropoda (snails), Bivalvia (clams), Cephalopoda (octopuses, squids).
Arthropoda (Arthropods): Bilateral symmetry; exoskeleton; segmented body; jointed appendages. Classes: Insecta (insects), Arachnida (spiders), Crustacea (crabs, lobsters).
Annelida (Segmented Worms): Bilateral symmetry; coelomates; segmented bodies. Classes: Oligochaeta (earthworms), Polychaeta (marine worms), Hirudinea (leeches).
Echinodermata (Echinoderms): Radial symmetry (in adults); coelomates; spiny skin; water vascular system. Classes: Asteroidea (starfish), Echinoidea (sea urchins), Holothuroidea (sea cucumbers).
Chordata (Chordates): Bilateral symmetry; coelomates; have a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail. Subphyla: Vertebrata (vertebrates), Cephalochordata (lancelets), Urochordata (tunicates).

Question 50

What are hemichordates?

Answer 50

Hemichordates are a group of marine animals that share some features with chordates, including a dorsal nerve cord and pharyngeal slits, but they lack a notochord. They include acorn worms and pterobranchs.

Question 51

Name the four characteristics that all Chordates share

Answer 51

Notochord: A flexible rod that provides support.
Dorsal Hollow Nerve Cord: A nerve cord located along the back.
Pharyngeal Slits: Openings in the throat region that are used for filter feeding or respiration.
Post-anal Tail: An extension of the body beyond the anus that is present at some stage in development.