1108 Biology Animal Review

Analogies

Characters that can evolve more than once in separate groups by convergent evolution

Homologies

Characters that are similar due to common ancestry

Poriferans

The phylum that is made up of sponges

Cnidarians

The phylum that contains jellyfish and sea anemones

Radial symmetry

Organisms who's bodies have an axis that runs from mouth to base with many planes of symmetry through this axis; usually organisms like this are in the phylum cnidaria

Bilateral symmetry

Organisms who's bodies have a distinct head and tail, marking front and back, with a single plane of symmetry running between them at the midline; animals like this are clustered in the Bilateria branch

Acoelomates

Bilaterians without a body cavity

Coelomates

Bilaterians with a body cavity

Pseudocoelomates

Bilaterians with a body cavity that does not completely surround the internal organs

What does a fluid-filled body cavity do?

It cushions the internal organs against hard blows to the body and enables the body to turn without twisting these organs. It also allows internal organs like the stomach to expand, enhancing digestive function

Diploblastic

Cnidarian embryos that have two germ layers, the ectoderm and the endoderm.

Triploblastic

Bilateral embryos that have three germ layers, the ectoderm, endoderm and misoderm

Protostomes

The first opening to the internal cavity of cavity of the developing embryo, called the blastopore, becomes the mouth

What happens to the blastopore in deuterostomes?

The blastopore becomes the anus

What are the two subgroups can the protostome phyla be divided into?

Lophotrochozoans and ecdysozoans

What are the characteristics of the cells on the outside of a sponge?

These cells are tough and act as the sponge's skin

Choanocytes

Cells that have a flagella and function in nutrition and gas exchange. They have a collar of small cilia around their flagellum; located in the interior of sponges

Mesohyl

A gelatinous mass (between the interior and exterior cell layers in a sponge) that is mostly noncellular, but does contains some amoeba-like cells that function in skeleton formation and the dispersal of nutrients

How do sponges gain nutrition?

Intracellular digestion; The choanocytes that surround the interior chamber of the sponge beat their flagella, creating a current that draws water from the outside the body, through the pores in its walls and upward through the central cavity of the sponge, where it exits through the large opening at the top. The water contains food particles and dissolved organic mater, which cells lining the cavity capture by endocytosis.

How do sponges reproduce?

Cells recruited from the choanocyte layer migrate into the mesohyl, where they undergo meiosis and differentiate as sperm or eggs. Sperm released into the water fuse with eggs in the meshy of other sponges.

Spicules

The simple structures that act as skeletons in sponges

True or False: Sponges do not form symbiotic relationships

False; Many sponges obtain at least part of their nutrition from symbiotic algae living within their bodies

Euetazoa

A clade comprising all major animal groups except sponges, placozoa, and several other extinct or obscure life forms, such as Iotuba and Thectardis.

Gastric cavity

The site of extracellular digestion and excretion in organisms like medusa (jellyfish) and polyps (anemone), that comes after the opening of the mouth in these animals.

What does the gastric cavity do?

Rather than digesting food particles inside individual cells, cnidarians receive both food and digestive enzymes in the gastric cavity (the digestive enzymes are secreted by cells that line the walls of the cavity). This arrangement permits cnidarians to digest large food items, like whole fish.

True or False: the cnidarian body develops from a diploblastic embryo

True

What does the cnidarian body consist of?

It has an outer layer, the epidermis, which develops from the ectoderm, and an inner lining, the endodermis, that derives from the endoderm. These tissues enclose a gelatinous mass called the mesoglea (the "jelly" of jellyfish)

Cnidarian vs sponge body plan

1. In cnidarians, the cells that form the epidermis and endodermis occur as closely packed layers of cells embedded in a protein-rich matrix, forming an epithelium, which often absorb or secrete substances into the compartments they line, making possible organs such as those of the digestive system

2. Cnidarians have a wider array of cell types than sponges do, permitting more sophisticated tissue function (like muscle cells or nerve cells)

3. Sponges filter water to gain food, while cnidarians are predators, capturing prey with their tentacles and digesting it in the gastric cavity

Nematocyst

A tiny harpoon-like organelles contained on specialized cells on the tentacles of cnidarians that is often tipped with a powerful neurotoxin, which greatly aids prey capture and defense against other predators

How is waste removal carried out in cnidarians?

Since there is no specialized passage for waste removal, waste is excreted back into the gastric cavity and leaves by the way of mouth.

True or false: Cnidarians don't reproduce asexually

Fasle; many cnidarians reproduce asexually to form colonies.

What are ctenophores and what do they have in common with cnidarians?

Ctenophores, or comb-jellies, resemble cnidarians in body plane, with radial symmetry, an outer epithelium and an inner endodermis that enclose a gelatinous interior. They also differentiate muscle cells and a simple nerve net. They also are predators that feed by ingestion, digesting prey within their gastric cavity by enzymes secreted from the cells lining the gut cavity.

Differences between cnidarians and comb-jellies

1. Comb-jellies have specialized cells on their tentacles that secrete adhesive molecules that entangle prey

2. Digestive wastes generated by comb-jellies move through a gut cavity for elimination through an anal pore opposite the mouth.

3. The pattern of muscle cell development in comb-jellies suggests that theses cells originate from a rudimentary mesoderm situated between the ectoderm and endoderm.

What is the benefit of having a digestive system that has an anterior-posterior axial arrangement?

This arrangement allows each section of the gut to be specialized for a particular function, such as temporary storage, digestion, and absorption and excretion, increasing the overall efficiency in processing food. Cnidarians digest and absorb and store food in the same pouch, and so are much less efficient.

Placozoans

Simple, tiny animals that each contain only a few thousand cells arranged into an upper and lower epithelia that sandwich an interior fluid crisscrossed by a network of multinucleate fiber cells

How do placozoans feed?

Placozoans can absorb dissolved organic molecules, but commonly feed by surrounding food particles and secreting digestive enzymes to break them down. Individual cells then bring food particles in by endocytosis

How do placozoans move, preform gas exchange, and reproduce?

They move by cilia on the cell surfaces, preform gas exchange by diffusion, and reproduce asexually, but can also form egg and sperm cells for sexual reproduction

How many phyla does the Locphotrohozoa contain?

17, mostly small marine animals of limited diversity, but it also includes the diverse and ecologically important annelid worms and mollusks

What are annelids?

The annelids most familiar to us are the earthworms. Most of the 15,000 known annelid species live in the oceans.

Annelid body plan

They have a cylindrical body with distinct segments, and they illustrate the advantages of a bilateral body plan. At one end, the head has a well-developed mouth and, internally, a cerebral ganglion (a collection of nerve cells) that connects to an extensive nervous system. A digestive system extends through the body from the head to an anus, with a sequence extends through the body from the head to an anus, with a sequence of specialized organs for crushing, then digesting, and finally excreting ingested food, much like the digestive system in our own bodies. Annelids have waste-filtering organs called nephridia, gonads (repeated in most segments), and a fluid-filled coelom, or body cavity. Fluids in the coelom form a hydrostatic skeleton that works in coordination with paired muscles in each segment to direct movement

How do annelids preform gas exchange?

Aquatic annelids have gill-like organs for gas exchange, but terrestrial earthworms exchange gases through their skin. In both cases, a closed circulatory system moves dissolved gases through the body.

How do annelids feed?

Many annelids are predators that capture and ingest prey, but some, like earthworms, ingest sediment, digesting the organic matter it contains and excreting mineral particles. A few marine annelids have evolved tentacles that enable them to filter food particles from water, while leeches, a specialized group of freshwater annelids, attach themselves to vertebrates to such out a meal of blood.

How do meter-long vestimentiferan worms feed?

Vestimentiferan worms that live around hydrothermal vents in the oceans have given up ingestion altogether. Without mouths, these enormous worms gain nutrition from chemosynthetic bacteria that live within a collar of specialized tissue.

What are mollusks?

They are a major phylum of the Lophotrochozoa

Gastropods

Snails and slugs

Gastropod body plan

They have a head with a well-developed mouth that contains a toothlike structure called a radula for feeding. The mouth connects to a gut cavity that extends to an anus. Feather-like gills facilitate gas exchange, and a muscular foot used for locomotion. A neural ganglion in the head coordinates a nervous system that extends through a body that also contains a well-developed circulatory system, gonads, and nephridia.

Are gastropods coelomates?

Yes, but the body cavity is generally reduced to small pouches that surround the heart and other organs.

What is the mantle in a gastropods?

The outer surface of the body; In gastropods the mantle tissues secrete external skeletons of calcium carbonate, which form shells.

How do gastropods feed?

Some gastropods eat algae, but many are predators.

Where do gastropods live?

About half occur in the ocean, and the other half are freshwater and terrestrial species the feed primarily feed on plants. In land snails and slugs, the only terrestrial mollusks, the gills have been lost, and gas exchange occurs in an internal cavity that has been modified to function as a lung.

Cephalopods

A class of mollusks with about 700 species of squid, cuttlefish, octopus and the chambered nautilus

What do cephalopods and gastropods have in common?

Much of their internal anatomy, feather-like gills, and mantle

What distinguishes cephalopods?

They have muscular tentacles that capture prey and sense the environment. These leg like appendages are found on the head.

How do cephalopods swim?

They dart through the water by means of jet propulsion system that forces water through mantle tissue that is fused to form a siphon.

What makes cephalopods important predators in the oceans?

The combination of tentacles and rapid locomotion. Also, they have exceptional eyesight and exhibit the most complex behavior of any invertebrate animals, able to learn visual patterns and solve puzzles to gain food

True or False: All cephalopods have shells

False; Some, like squids and octopus, have little or no shell

What are the bivalves?

Animals (like clams, oysters, and mussels) that have no head, by two hard shells called valves that are connected by a flexible hinge

How do most bivalves obtain food?

By filtering particles from seawater

How do bivalves that burrow their bodies into sand or mud feed?

They have a modified mantle that consists of fused mantle tissue that form a pair of siphons that extend upward from the bivalve's body to the surface of the seafloor above it. One siphon draws water containing food and oxygen into the body, while the second one returns the water and waste materials to the environment.

Where do ecdysozoa get their name from?

From the process of ecdysis or molting. All ecdysozoans secrete a cuticle made of protein that covers their bodies. This tough cuticle is like a suit of flexible, lightweight armor, protecting bodies from injury and physical challenges of the environment such as drying.

What special property does the cuticle have?

The hard cuticle can be used to form appendages that function as tools, weapons, or even wings.

Why do ecdysozoans molt their cuticle?

The cuticle is like a suit of armor. It is a perfect fit for the wearer, but it doesn't stretch, so it must be exchanged episodically during growth for a larger size to fit a larger, growing body.

Anthropoda

Phyla included under the Ecdosozoa that includes insects, containing half of all the known animals

Features of anthropods

They have jointed legs and a hard external skeleton, made of chitin

What are the four main types of anthropods?

Insects, chelicerates (spiders, scorpions), myriapods (centipedes and millipedes), and crustaceans (lobsters, shrimp, crabs)

Features of chelicerates

They don't have antennae; They are mostly carnivores (except for plant eating mites); Some are venomous

Features of myriapods

Many pairs of legs

Crustaceans

They have branched legs; highly sensory antennae

True or False: Birds were the first animals to evolve wings

False: Insects were, nearly 350 mya

Metamorphosis

A major change in form from one developmental stage to another; The body changes from a wormlike larva specialized for feeding to a stage called a pupa

Pupa stage

The body tissues undergo a remarkable transformation from the relatively simple larva to a very different looking adult such as a fly, butterfly, wasp, or beetl

Insect egg qualities

They have highly specialized eggshells that can withstand desiccation while still allowing gas exchange

Spiracles

Small pores on insects where gas exchange takes place

Tracheae

Internal system of tubes, where the spiracles connect, that direct oxygen to and remove carbon dioxide from respiring tissues in insects

Three major Deuterostomia phyla

Chordata, Hemichordata, and Echinodermata

Hemichordates

Include acorn worms; All have a mouth on an elongate protuberance called a proboscis that connects to the digestive tract by a tube called the pharynx, which contains a number of vertical openings called pharyngeal slits separated by stiff rods of proteins. They also have a dorsal nerve cord

Echinoderms

Include sea stars and sea urchins, sea cucumbers; They share a unique fivefold symmetry on top of their basic bilateral organization. They also form distinctive skeletons made of interlocking plates or porous calcite, a form of calcium carbonate. The third unique feature is the water vascular system, a series of fluid-filled canals that permits bulk transport of oxygen and nutrients. Tube feet, small projections of the water vascular system that extend outward from the body surface, facilitate locomotion, sensory perception, food capture, and gas exchange

Three subphyla of Chordata

Celphalochordates, tunicates, and vertebrates

Chordate features

They have a pharynx with pharyngeal slits (gills in fish). The notochord, a stiff rod of collagen and other proteins, runs along the back, providing support for the axis in some chordates. In vertebrates, the notochord is apparent only during early embryogenesis and is replaced functionally by the development of a neural tube, a cylinder of embryological tissue that develops into a dorsal nerve cord. Chordates have a tail that extends posterior to the anus and muscularized appendages that include the fins of fish and legs of terrestrial vertebrates

Tunicate

The adult body is a basket-like structure that is highly modified for filter-feeding. The body wall has a siphon-like mouth at one end that draws water through an expanded pharynx that captures food particles. Water and wastes are expelled through an anal siphon.

Why are some animals called vertebrates?

They have a jointed skeleton that runs along the main axis of the body, forming a series of hard segments collectively termed vertebrae.

How are vertebrate animals distinguished?

They have a cranium that protects a well-developed brain, a pair of eyes, a distinctive mouth for food capture and ingestion, and an internal skeleton commonly mineralized by calcium phosphate. They also have a coelom in which the organs are suspended, and a closed circulatory system.

Lamprey and hagfish

These animals have a cranium built of cartilage but lack jaws. Lampreys also have a vertebral column built of cartilage. Hagfish lack vertebrae.

Chondrichthyes

Cartilaginous fish; all have jaws and a skeleton made of cartilage (sharks)

Osteichthyes

Bony fish; they have a cranium, jaws, and bones mineralized by calcium phosphate (the fish we usually encounter); They have a system of movable elements in their jaws that allows them to specialize and diversify their feeding; The possess a swim bladder that controls their position in water; They have kidneys

Tetrapod

4 legs

Where do amphibians reproduce?

Water

Amniotic egg

Can exchange gases while retaining water, and also permits the group of vertebrates known as amniotes (lizards, snakes, turtles, crocodiles) to live in dry terrestrial habitats that amphibian eggs cannot tolerate

Mammals

Covered with hair and feed their young milk from mammary glands

Which of the following is not a characteristic exclusively found in animals?

A) chitin

B) collagen


C) multicellularity


D) gastrula

A) Chitin

Unlike cnidarians, the comb jellies have an anterior-posterior axis (an 'up' and 'down' orientation). This orientation allows for \__________________ in comb jellies.

A) directed gas exchange

B) tentacle attachment

C) differentiated muscle cells

D) more efficient nutrient digestion

D) more efficient nutrient digestion

Sponges move huge volumes of water through their bodies every day. Although this serves the function of filter feeding for the organism, how might this also provide an "ecosystem service" (something that affects and/or benefits other organisms in their environment)?

A) Their body chambers serve as places where smaller organisms can live and be protected from certain predators.

B) They produce large numbers of gametes that will become food for other sponges.

C) They create small currents in their micro-environment that help to circulate and clean water locally.

D) They can filter small poisonous fish out of the water that may harm other organisms.

C) They create small currents in their micro-environment that help to circulate and clean water locally.

The Cambrian Explosion of biodiversity occurred in what era?

A) Dinosaurozoic

B) Cenozoic

C) Proterozoic

D) Paleozoic

E)Mesozoic

D) Paleozoic

In which taxonomic group do sponges belong?

A) Porifera

B) Choanoflagellate

C) Cnidaria

D) Ctenophora

A) Porifera

Biologists have described about \_____ species of eukaryotic organisms, of which about \_____ are animals. The majority of these are \_____.

A) 30 million; 1 million; insects

B) 1.8 million; 1.3 million; insects

C) 1.8 million; 500,000; plants

D) 30 million; 500,000; plants

E) 1 million; 500,000; vertebrates

B) 1.8 million; 1.3 million; insects

Comparative embryology helped clarify the relationships among major groups of animals. The bilaterians, for example, can be divided into the \_____ based on the developmental fate of the blastopore.

A) cnidarians and radiolarians

B) coelomates and
pseudocoelomates

C) coelomates and acoelomates

D) protostomes and deuterostomes

E) protostomes and coelomates

D) protostomes and deuterostomes

The myriapods include the \_____, which are fast-moving predators with front legs modified into venomous fang-like organs, and \_____, which are slow-moving herbivores.

A) scorpions; millipedes

B) centipedes; millipedes

C) spiders; mites

D) centipedes; mites

E) millipedes; centipedes

B) centipedes; millipedes

Cnidarians are able to capture prey with the aid of \_____, harpoon-like organelles that are often tipped with neurotoxins.

A) polyps

B) choanocytes

C) nematocysts

D) mesoglea

C) nematocysts

\_____, which include lobsters and crabs, have \_____ legs and, in the ocean, fill many of the ecological roles filled by insects on land.

A) Crustaceans; unbranched

B) Chelicerates; branched


C) Chelicerates; unbranched

D) Crustaceans; branched

D) Crustaceans; branched

What is the predominant hypothesis why animals only appeared in the fossil record about 3 billion years after life originated?

A) Animals are heterotrophic and couldn't evolve until there were enough photosynthetic organisms on Earth to support being eaten by animals.

B) Animals are warm-blooded, the ocean was too cold for animals to evolve 3 billion years ago.

C) There were animals 3 billion years ago, they just weren't fossilized.


D) Animals have higher metabolisms, and animal diversification and evolution didn't really happen until there was sufficient oxygen in the atmosphere.

D) Animals have higher metabolisms, and animal diversification and evolution didn't really happen until there was sufficient oxygen in the atmosphere.