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Biology Ch. 18

Multicellular, heterotrophic (cannot make their own food) eukaryotes that obtain nutrients by ingestion (eating food)
eating food.
within their body
Animals digest food WHERE after ingesting other organisms. This mode of nutrition contrasts animals with fungi, which absorb nutrients after digesting food outside their body.
cell wall
Animal cells lack the WHAT the provide strong support in the bodies of plants and fungi.
extracellular structural proteins
Animals cells are held together by WHAT and by unique types of intercellular junctions
Most animals cells are WHAT and reproduce sexually?
Eggs and sperm are the only WHAT cells?
Animal Life Cycle
1. Male and Female adult animals make haploid gametes by meiosis. 2. An egg and a sperm fuse, producing a zygote. 3. This zygote divides by mitosis, forming a blastula (an early embryonic stage, which is a hollow ball of cells). 5. One side of the blastula folds inward, forming a stage called gastrula. 6. The internal sac formed by gastrulation becomes the digestive tract, lined by a cell layer called the endoderm, ectoderm, and mesoderm. 7. After the gastrula stage, many animals develop into adults but some animals (like the sea star) develop into a larva. 8. Then metamorphis
An early embryonic stage- usually a holllow ball of cells
One side of the blastula folds inward, forming a stage called WHAT?
The internal sac formed by gastrulation becomes the digestive tract, lined by a cell layer called WHAT?
An outer cell layer that gives rise to the outer covering of the animal and, in some phyla, to the central nervous system.
A third embryonic layer that forms the muscles and most other internal organs
An immature individual that looks different from the adult animal.
The larva undergoes a major change of body form called what?
List the distinguishing characteristics of animals
List the distinguishing characteristics of animals: Multicellular, eukaryotic heterotrophs that ingest their food; no cell walls; unique cell junctions; nerve and muscle cells; sexual reproduction and life cycles with unique embryonic stages; unique developmental genes
hox genes
All eukaryotes have regulatory genes that contain DNA sequences called homeoboxes. But animals share a unique homeobox containing family of genes called WHAT that play important roles in the development of animal embryos. (DNA blueprint)
Some molecular clock calculations estimate that the common ancestor of living animals lived about a billion years ago. This ancestor may have resembled modern WHAT, colonial protists that are the closest living relatives of animals
Hypothesis for how choanoflagellates may have evolved into an animal
Hypothesis for how choanoflagellates may have evolved into an animal: 1. The earliest colonial aggregates may have been only a few cells. 2. Some larger colonies may have formed hollow spheres. 3. Eventually, cells in the colony may have become specialized for functions such as reproduction, locomotion, and feeding. 4. A simple multicellular organism with cell layers might have evolved as cells on one side of the colony folded inward. 5. Eventually, a gastrula-like "proto-animal" may have evolved.
575 million years
The oldest known animal fossils date from the late Precambrian time, about HOW long ago?
Cambrian Explosion
Dramatic increase in animal diversity. So many animal body plans and new phyla appear in such an evolutionarily short time span that biologists call this WHAT?
1 causation of Cambrian explosion
1 causation of Cambrian Explosion: The evolution of hard body coverings led to increasingly complex predator-prey relationships and diverse adaptations for feeding, motility, and protection.
2 causation of Cambrian Explosion
2 causation of Cambrian Explosion: Focuses on geologic changes- Atmospheric oxygen had finally reached a high enough concentration to support the metabolism of more active, mobile animals.
Lack a vertebral column (backbone).
radial symmetry
Body parts radiate from the center. Any imaginary slice through the central axis divides a radially symmetrical animal into mirror images.
bilateral symmetry
mirror-image right and left sides. Ex.) lobster
A distinct head, or WHAT?
a tail or what?
The symmetry of an animal fits its WHAT? A radial animal is typically sedentary or passively drifting, meeting its environment equally on all sides. In contrast, most bilateral symmetrical animals are active and travel headfirst through the environment.
true tissues
Collections of specialized cells, usually isolated from other tissues by membrane layers, that perform specific functions. Ex.) the nervous tissue of your brain and spinal cord)
three tissue layers
Some animals have only ectoderm and endoderm; most animals also have mesoderm, making a body with WHAT?
body cavity
Animals with three tissue layers may be characterized by the presence or absence of a WHAT? This fluid-filled space between the digestive tract and body wall cushions the internal organs and enables them to grow and move independently.
hydrostatic skeleton
In soft-bodied animals, a noncompressible fluid in the body cavity forms a WHAT that provides a rigid structure against which muscles contract, moving the animal.
body covering
tissue-filled region
digestive sac
A roundworm has a body cavity called WHAT? This is not completely lined by tissue derived from mesoderm.
A segmented worm has a body cavity called a true WHAT, which is completely lined by tissue derived from mesoderm.
embryonic development
Animals with three tissue layers can be separated into two groups based on details of their WHAT, such as the fate of the opening formed during gastrulation that leads to the developing digstive tract.
The opening becomes the mouth. Bilaterally symmetrical and 3 tissue layer. (Flatworms, Molluscs, Annelids, Arthropods, nematodes)
Opening becomes the anus, and the mouth forms from a second opening. (Echinoderms, Chordates)
List four features that can describe an animal's body plan
List four features that can describe an animal's body plan: Symmetry, number of tissue layers, body cavity type, embryonic development
biologists have proposed hypotheses about animal phylogeny based on morphological studies, often using the characteristics of body plan and embryonic development described in the preceding module.
The first branch splits the sponges from the clade of WHAT, the animals with true tissues.
The next branch point separates the animals with radial symmetry from those with bilateral symmetry.
deuterostomes and protostomes
This morphology-based tree then divides the bilaterians into two clades based on embryology...
stationary animals that are so sedentary that the ancient Greeks believed them to be plants. Majority of the species are marine, although some are found in fresh water. Have folded body walls and irregular shapes. Lack body symmetry, but some radically symmetrical.
choanocytes and amoebocytes
The body of a sponge consists of TWO LAYERS of cells separated by a gelatinous region.
Inner layer of flagellated cells. Help to sweet water through the sponge's body.
Wandering through the middle body region are WHAT, which produce skeletal fibers composed of either mineral-containing particles or a flexible protein called spongin.
suspension feeders
Spongers are examples of this (also known as filter feeders), animals that collect food particles from water passed through some type of food-trapping equipment.
Adult sponges are this, meaning they are anchored in place; therefore, they cannot escape from predators.
Sponges are the WHAT of all animals. They have no nerves or muscles, though their individual cells can sense and react to changes in the environment.
Why is it thought that sponges represent the earliest branch of the animal kingdom
Why is it thought that sponges represent the earliest branch of the animal kingdom: Sponges lack symmetry and true tissue, and their choanocyte resemble certain flagelleta protists.
All animals except sponges have true tissue and belong to the clade WHAT?
One of the oldest groups is this phylum and includes the hydras, jellies, sea anemones, and corals
Characterized by radial symmetry and only two tissue layers. The simple body of most cnidarians has an outer epidermis and an inner cell layer that lines the digestive cavity.
Hydras, common in freshwater ponds and lakes, have a cylindrical body with tentacles projecting from one end. This body form is a WHAT?
Exemplified by the marine jelly. Moves freely in the water while polyps are mostly stationary.
Cnidarians are carnivores that use their WHAT to capture small animals and protists and to push the prey into their mouths.
gastrovascular cavity
The mouth is the only opening in the body, so undigested food and other wastes exit through it. The gastrovascular cavity also circulates fluid that services internal cells. Fluid in the cavity also provides body support and helps give a cnidarian its shape (ex. water in a balloon)
Unique stinging cells that function in defense and in capturing prey. Each cnidocyte contains a fine thread coiled within a capsule. When it is discharged, the thread can sting or entangle
What are three functions of a cnidarian's gastrovascular cavity?
What are three functions of a cnidarian's gastrovascular cavity?: 1. Digestion, 2. Circulation 3. Physical support and movement
Phylum Platyhelminthes are the simplest of the bilaterians. These thin, often ribbonlike animals range in length from about 1 mm to 20 m and live in marine, freshwater, and damp terrestrial habitats. In common with cnidarians, most flatworms have a gastrovascular cavity with only one opening.
planarian, flukes, and tapeworms
what are the three major groups of flatworks?
Represent a group known as free-living flatworms. It has a head with a pair of light-sensitive eyespots and a flap at each side that detects chemicals. Dense clusters of nerve cells form a simple brain, and a pair of nerve cords connect with small nerves that branch throughout the body. Live on the undersurfaces of rocks in freshwater ponds and streams.
Gastrovascular cavity of a planarian is highly WHAT?
Planarians use WHAT on their ventral surface, they crawl about in search of food. They also have muscles that enable them to twist and turn.
A second group of flatworms which live as parasites in other animals. Many of these have suckers that attach to their host and a touch protective covering. Reproductive organs occupy nearly the entire interior of these worms.
Many flukes have complex life cycles with an intermediate host in which larvae develop. The WHAT then infect the final host in which they live as adults
another parasitic group of flatworms. Adult tapeworms inhabit the digestive tracts of vertebrates, including humans. (Always found within a host).
repeated units
In contrast with planarians and flukes, most tapeworms have a very long, ribbonlike body with WHAT? They also differ from other flatworms in not having a digestive tract. Living in partially digested food in the intestines of their hosts, they simply absorb nutrients across their bod surface.
The anterior end, called that WHAT, is armed with hooks and suckers that grasp the host in tapeworms
life cycle
Like parasitic flukes, tapeworms have a complex WHAT, usually involving more than one host.
Humans can be infected with tapeworms by eating WHAT pork or beef infected with tapeworm larvae.
Also called roundworms, make up the phylum nematoda. As bilaterians, these animals have bilateral symmetry and a three-tissue layer construction. In contrast with flatworms, roundworms have a fluid-filled body cavity (a pseudocoelom, not completely lined with mesoderm) and a digestive tract with two openings.
Nematodes are WHAT with a blunt head and tapered tail. They range in size from less than 1 mm to more than a meter.
Nematodes' body is covered by a tough, nonliving covering, or WHAT, that resists drying and crushing. When the worm grows, it periodically sheds and secrets a new, larger one.
complete digestive tract
Nematodes have WHAT, extending as a tube from the mouth to the anus near the tip of the tail. Food travels only one way through the system and is processed as it moves along. In animals with a complete digestive tract, the anterior regions of the tract churn and mix food with enzymes, while the posterior regions absorb nutrients and then dispose of wastes. This division of labor allows each part of the digestive tract to be specialized for its particular function.
anterior regions
Complete digestive tract- churn and mix food with enzymes
posterior regions
Complete digestive tract- absorb nutrients and then dispose of wastes.
Nematodes are among the most numerous of all animals in both number of species and number of individuals. Nematodes live virtually everywhere there is rotting organic matter. These worms are important WHAT in soil and on bottom of lakes and oceans.
Why does a nematode have to shed its cuticle when it grows?
Why does a nematode have to shed its cuticle when it grows?: This nonliving cuticle does not expend as the animal grows. The nematode must molt its old cuticle and secrete a new, large one.
Snails, slugs, oysters, clams, octopuses, and squids are just a few of the great variety of animals known as WHAT. They are soft bodied animals, but most are protected by a hard shell.
foot, visceral mass, and mantle
Basic body plan of a mollusc consists of 3 main parts:
functions in locomotion
visceral mass
contains most of the internal organs
a fold of tissue that drapes over the visceral mass and secretes a shell in molluscs such as clams and snails.
mantle cavity
In many molluscs, the mantle extends beyond the visceral mass, producing a water-filled chamber called the WHAT, which houses the gills.
A unique rasping organ called WHAT which is used by molluscs to scrape up food.
The life cycle of many marine molluscs includes a ciliated larva called a WHAT, which is also characteristic of some other invertebrate phyla.
true coelom
In contrast with flatworms, which have no body cavity, and nematodes, which have a pseudocoelom, molluscs have a WHAT?
circulatory system
Also unlike flatworms and nematodes, molluscs have a WHAT- an organ system that pumps blood and distributes nutrients and oxygen throughout the body.
gastropods, bivalves, and cephalopods
3 groups of molluscs:
The largest group of molluscs. Found in freshwater, salt water, and terrestrial environments. Most of these are protected by a single, spiraled SHELL into which the animal can retreat when threatened. Many of these have a distinct head with eyes at the tips of tentacles, like the land snail
Molluscs that include numerous species of clams, oysters, mussels, and scallops. They have shells divided into two halves that are hinged together. Most bivalves are suspension feeders. Most bivalves are sedentary, living in sand or mud.
Differ from gastropods and bivalves in being adapted to the lifestyle of fast, agile predators. External shells, small and internal shells, or missing all together. Cephalopods use beat-like jaws and a radula to crush or rip prey apart. All cephalopods have large brains and sophisticated sense organs, and these contribute to their being successful, mobile predators. Very intelligent. ex.) squid and octopus
the subdivision of the body along its length into a series of repeated parts (segments).
An earthworm, a typical WHAT, uses its flexible, segmented body to crawl and burrow rapidly into the soil. Range in length from less than 1 mm to 3m. They are found in damp soil, in the sea, and in most freshwater habitats
earthworms, polychaetes, and leeches
3 main groups of annelids:
Earthworm is partitioned by membrane walls.
nervous system
Earthworms- includes a simple brain and a ventral nerve cord with a cluster of nerve cells in each segment. (Internal body structures are repeated within each segment)
Excretory organs
Earthworms- dispose of fluid wastes, are also repeated in each segment. (Internal body structures are repeated within each segment)
digestive tract
Earthworms- this tract is not segmented; it passes through the segment walls from the mouth to the anus.
open circulatory system
Many invertebrates, molluscs, and all arthropods have this in which blood is pumped through vessels that open into body cavities where organs are bathed directly in blood.
closed circulatory system
Annelids and vertebrates have this, in which blood remains enclosed in vessels as it distributes nutrients and oxygen throughout the body.
longitudinal and circular
Each segment in earthworms is surrounded by WHAT and WHAT muscles. Earthworms move by coordinating the contraction of these two sets of muscles. These muscles work against the coelomic fluid in each segment, which acts as a hydrostatic skeleton.
Earthworms are this which means they have both male and female reproductive structures. But they mate and cross-fertilize by exchanging sperm.
Earthworms eat their way through what, extracting nutrients as soil passes through their digestive tube. Undigested material, mixed with mucus secreted into the digestive tract, is eliminated as castings (fecus) through the anus. Farmers value earthworms bc it improves soil's texture
Form the largest group of annelids. Each segment of a polychaete has a pair of fleshy, paddle-like appendages with many stuff bristles (called chaetae) that help the worm wiggle about in search of small invertebrates to eat. In many polychaetes, the appendages are richly supplied with blood vessels, and function in gas exchange.
The third main group of annelids- notorious for their bloodsucking habits. They range in length from 1 to 30 cm. Some bloodsucking leeches use razor-like jaws to slit the skin of an animal. The host is usually oblivious to this attack because the leech secrets an anesthetic (numb the location) as well as an anticoagulant (keep from blood clotting) into the wound.
good use for leeches
Leeches are still occassionally used to remove blood from bruised tissues and to help relieve swelling in fingers or toes that have been sewn back on after accidents. Blood tends to accumulate in a rearrached finger or toe until small veins have a chance to grow back into it. Leeches are applied to remove this blood.
Tapeworms and leeches are both parasites. What are the key differences between the two?
Tapeworms and leeches are both parasites. What are the key differences between the two?: Whereas both are composed of repeated segments, the segments of a tapeworm are filled mostly with reproductive organs and are shed from the posterior end of the animal. Tapeworms are flatworms with no body cavity and, in their parasitic lifestyle, not even a gastrovascular cavity. Leeches have a true coelom and a complete digestive tract.
Includes crayfish, lobsters, crabs, barnacles, spiders, ticks, and insecrets. In terms of species diversity, geographic distribution and numbers, phylum Arthropoda must be regarded as the most successful animal phylum.
The arthropod body, including the appendages, is covered by an WHAT- an external skeleton that protects the animal and provides points of attachment for the muscles that move the appendages. This nonliving covering, or cuticle is constructed from layers of protein and chitin, a polysaccharide. The exoskeleton is thick around the head, where its main function is to house and protect the brain.
As the exoskeleton grows, an arthropod must periodically shed its old exoskeleton and secrete a larger one, a process called WHAT?
In contrast with annelids, which have similar segments throughout their body, the body of most arthropods is formed of several distinct groups of WHAT: the head, thorax, and abdomen
Arthropod- bears sensory antennae, eyes and jointed mouthparts on the ventral side.
Arthropod- bears a pair of defensive appendages (the pncers) and four pairs of legs for walking.
Arthropod- has swimming appendages
open circulatory system
Unlike annelids, arthropods have WHAT in which a tube-like heart pumps blood through short arteries into spaces surrounding the organs. Most aquatic species have gills. Terrestrial insects have internal air ducts that branch throughout the body.
horseshoe crabs are this. One of the oldest animals on earth. They also include scorpions, spiders, ticks, mites are called arachnids.
A type of chelicerate that lives on land. Scorpions, spiders and mites.
Arthropods- worm like terrestrial creatures that eat decaying plant matter. They have TWO pairs of short legs per body segment.
Arthropods- terrestrial carnivores with a pair of poison claws used in defense and to paralyze prey, such as cockroaches and flies. Each of their body segments bears ONE pair of legs
Arthropods- nearly all are aquatic. Lobsters and crayfish are in this group, along with numerous crabs, shrimps, and barnacles.
chelicerates, millipedes, centipedes, and crustaceans
arthropods have 4 different groupings:
Insects comprise about 70% of all animal species
a branch of biology that specializes in the study of insects.
Insects- usually bears a pair of sensory antennae and a pair of eyes. Several pairs of mouthparts are adapted for particular kinds of eating.
three-part body
Each embryonic segment is a separate building block that develops independently. Insects have a three-part body: head, thorax, and abdomen.
three, two
Most adult insects have # pair of legs and # pair of wings.
Insects ability to WHAT is a major factor in their success.
incomplete metamorphosis
The young resemble adults but are smaller with different body proportions. (No pupa stage)
complete metamorphosis
Larval stages are specialized for eating and growing and look very different from the adults, which are specialized for dispersal and reproduction. (Ex. Caterpillars which are the larvae of butterflies)
sea stars, sand dollars, and sea urchins, are slow-moving or sessile marine animals. Most are radially symmetrical as adults.
Echinoderms have prickly bumps or spines of a sea star or sea urchin. These are extersions of the hard calcareous plates that form the WHAT, or internal skeleton, under the thin skin of the animal.
water vascular system
A network of water-filled canals that branch into extensions called tube feet. Tube feet function in locomotion, feeding, and gas exchange.
Sea stars and some other echinoderms are capable of WHAT? Arms that are lost are readily regrown.
Contrast the skeleton of an echinoderm with that of an arthropod
Contrast the skeleton of an echinoderm with that of an arthropod: An echinoderm has an endoskeleton, an arthropod has an exoskeleton.
ur distinctive features appear in Chordata
Four distinctive features appear in Chordata: 1. Dorsal, hollow nerve chord 2. A notochord. 3. Pharyngeal slits. 4. post-anal tail
a flexible, supportive, longitudinal rod located between the digestive tract and the nerve chord
pharyngeal slits
located in the pharynx, the region just behind the mouth
post-anal tail
a tail posterior to the anus
Chordata- stationary and look more like small sacs. They often adhere to rocks and boats, and they are common on coral reefs. The adult has no trace of a notochord, nerve chord, or tail, but it does have prominent pharyngeal slits that function in feeding.
Another group of marine invertebrate chordates, also feed on suspended particles. They are small, bladelike chordates that live in marine sands.
What 4 features do we share with invertebrate chordates, such as lancelets?
What 4 features do we share with invertebrate chordates, such as lancelets?: 1. Dorsal, hollow nerve chord 2. notochord 3. pharyngeal slits 4. post-anal tail