Biology chapter 18
animals
-multicellular -heterotrophic eukaryotes -obtain nutrients by ingestion
Earthworms are most closely related to _____. A leeches B sea urchins C roundworms D tapeworms
A
How do coral animals obtain their food? A tentacles that trap smaller animals and protists B absorption of predigested food through their cuticle C photosynthesis D by eating plants
A
The phylum _____ includes the largest number of species of all animal phyla. A Arthropoda B Annelida C Chordata D Mollusca
A
The two major groups of protostomes in the "new" phylogeny of animals are _____. A Lophotrochozoa and Ecdysozoa B Bilateria and Deuterostomia C Metazoa and Eumetazoa D radially and bilaterally symmetrical animals
A
Leeches are members of the phylum _____. A Cnidaria B Annelida C Nematoda D Platyhelminthes
B
An active marine predator is found possessing these characteristics: a series of tentacles (modified from the foot), a highly developed nervous system, and elaborate image-forming eyes. This organism is most likely a(n) _____. A radularian B arachnid C cephalopod D gastropod
C
An animal is called a protostome or a deuterostome based on _____. A whether it has a body cavity B the number of germ layers it has C the way its body cavity develops D the presence or absence of a mouth
C
Animals of one common phylum are NOT bilaterians but ARE eumetazoans. What phylum is it? A Chordata B Porifera C Cnidaria D Annelida
C
The majority of animal species are _____. A marine B deuterostomes C insects D vertebrates
C
Which of the following animals is most closely related to spiders? A lobsters B grasshoppers C scorpions D millipedes
C
Which of the following is thought to be most closely related to humans? A jellies B snails C sea stars D earthworms
C
A _____ is a chordate but not a vertebrate. A sea star B lamprey C shark D lancelet
D
Choose the option that correctly matches each mollusc class to its typical lifestyle. A gastropods = sedentary suspension feeders, bivalves = ambush predators, and cephalopods = active predators B gastropods = slow-moving algae scrapers, bivalves = sedentary suspension feeders, and cephalopods = sessile herbivores C gastropods = slow-moving algae scrapers, bivalves = terrestrial decomposers, and cephalopods = active predators D gastropods = slow-moving algae scrapers, bivalves = sedentary suspension feeders, and cephalopods = active predators
D
The water vascular system of a sea star functions in _____. A pumping water for swimming movements B waste disposal C digestion D movement of the tube feet
D
Which chordate is a stationary, globular suspension feeder as an adult? A sponge B bivalve C lancelet D tunicate
D
What is the difference between complete and incomplete metamorphosis? Insects that undergo incomplete metamorphosis have a modular body plan. For insects that undergo incomplete metamorphosis, the juveniles always resemble the adults. Insects that undergo incomplete metamorphosis do not form larvae. Insects that undergo incomplete metamorphosis do not form pupae.
Insects that undergo incomplete metamorphosis do not form pupae.
Biology deals with many kinds of worms. Which choice includes three different phyla of "worms"? Nematoda, Cnidaria, Oligochaeta Cnidaria, Arthropoda, Corals Platyhelminthes, Annelida, Nematoda Nematoda, Platyhelminthes, Echinodermata
Platyhelminthes, Annelida, Nematoda
vertebrates
animals with back bone; only one phylum includes this
When comparing gene content and gene expression of homeotic genes in arthropods versus velvet worms, scientists discovered __________. - arthropods and velvet worms have the same set of genes but these are expressed more intensely in the arthropods than in the velvet worms - arthropods and velvet worms have a different set of homeotic genes, which causes them to develop differently - arthropods and velvet worms have the same set of homeotic genes and these are expressed similarly in both groups of animals - arthropods and velvet worms have the same set of genes, but these are expressed at different body locations in each group of animals
arthropods and velvet worms have the same set of genes, but these are expressed at different body locations in each group of animals
spoges movement
cant move; are sessile; produce toxins and antibiotics to deter pathogens, parasites, and predators
endoderm
cell layer along the digestive tract
second hypothesis of why the arthropod body plan is successful
changes in the regulation of homeotic gene expression (when and where the genes are transcribed and translated into proteins) led to the diversity of segment and appendage types in arthropods; Such changes in developmental genes are known to result in significant morphological changes; proven true
Sea daisies are tiny marine animals found in deep water. These animals have a water vascular system, overlapping skeletal plates, and calcareous spines. Which of the features below would you expect them to also possess in the adult stage? no body cavity bilateral symmetry deuterostome development protostome development
deuterostome development
Fascioloides magna is an animal that lives in the livers of deer in the southeastern United States. It has a bilaterally symmetrical, flattened leaf-like body with a digestive tract with a single opening. It also lives in a snail for part of its life cycle. This animal is most likely a _____. roundworm tapeworm free-living flatworm fluke
fluke
Schistosomiasis is a debilitating disease that affects some 200 million people. It is caused by a parasitic flatworm that is transmitted to humans through contact with an air-breathing mollusc. The parasite and mollusc, respectively, are _____. tapeworms and bivalves free-living flatworms and bivalves flukes and snails tapeworms and snails
flukes and snails
three major group of flatworms
free living flatworms, flukes, tapeworms
At the Sand Bar restaurant, customers can nibble on snails (_____) with garlic butter and oysters on the half shell (_____) during their "happy hour." The happy patrons will be enjoying what types of molluscs? gastropods ... bivalves gastropods ... cephalopods bivalves ... cephalopods bivalves ... gastropods
gastropods ... bivalves
Pikaia gracilens is an extinct invertebrate animal described from the wonderful pre-Cambrian soft-bodied fossils of the Burgess Shale in British Columbia. Examinations by paleontologists have revealed that organisms belonging to this species had a prominent notochord and segmental muscles. From this information, you could conclude that it is closely related to __________. echinoderms molluscs annelids lancelets
lancelets
A medicinal annelid applied to drain blood from a patient. Children sometimes pick up "bloodsuckers" in ponds, but these segmented animals typically spend most of their time parasitizing turtles. Some are used medicinally to improve blood flow and reduce inflammation near injuries in humans. They are _____. leeches, a type of annelid leeches, a type of flatworm polychaetes, a type of annelid leeches, a type of roundworm
leeches, a type of annelid
flukes
live as parasites in other animals; nearly made up of reproductive organs; suckers that attach to their hosts;
ectoderm
outer cell layer that gives rise to the outer covering of the animal
polyps vs medusa
polyps are stationary but medusae move freely; polyp mouth is upward, medusae mouth is downwards
Dracunculus medinensis is a parasite that can grow to be one meter long, and which humans can acquire through contaminated drinking water. Which of the following traits would allow you to place this animal unambiguously in either the Platyhelminthes or Nematoda phyla? bilateral symmetry pseudocoelom lack of segmentation multicellular organization
pseudocoelom
nematodes
roundworms; phylum nematoda; bilateral symmetry with 3 tissue layers; in contrast with flatworms, roundworms have fluid filled body cavity (that functions to distribute nutrients) and a digestive tract with two openings; important decomposers in soil and on the bottom of lake and oceans
echinoderms
sea stars, sand dollars, sea urchins; slow moving or sessile marine animals; most are radially symmetric as adults; water vascular system (a network of water filled canals that branch into tube feet); tube feet functions in locomotion, feeding, and gas exchange; capable of regeneration; have endoskeleton of hard calcium-containing plates under a thin skin;
the arthropod body plan is a key factor in evolutionary success; how did this happen?
there were two hypothesis;
An animal has segments, bilateral symmetry, pharyngeal gill slits, a post-anal tail, and deuterostomic development. It must be a member of the phylum _____. A Chordata B Annelida C Arthropoda D Mollusca
A
Most animals are _____. A. flagellated unikonts B. invertebrates C. cephalopods D. chordates
B
Sea stars and sea urchins are members of the phylum _____. A Mollusca B Echinodermata C Annelida D Platyhelminthes
B
The animal phylum most like the protists that gave rise to the animals is _____. A Cnidaria B Porifera C Echinodermata D Platyhelminthes
B
Which characteristic is unique to Chordata (it is a diagnostic feature) and is evident at some stage of the life cycle in all chordates? A deuterostome development B notochord C the backbone D endoskeleton
B
Which correctly describes Echinodermata? A Most are bilaterally symmetrical as adults. B Larval forms show evidence of bilateral symmetry, which is later lost in the adult form. C Members of the phylum include the insects. D They are soft-bodied with neither an endoskeleton nor an exoskeleton.
B
Which of the following most clearly demonstrates the evolutionary relationship between nematodes and arthropods? A true tissues B a cuticle that must be shed by molting C jointed appendages D a complete digestive tract
B
A sea star and a sea jelly belong to the phyla _____ and _____, respectively. A Platyhelminthes ... Arachnida B Echinodermata ... Mollusca C Cnidaria ... Chordata D Echinodermata ... Cnidaria
D
In arthropods, molting is necessary because _____. A the environment degrades the exoskeleton, which therefore must be shed and replaced B arthropod appendages generally increase in number as the animal ages C the exoskeleton is progressively reabsorbed by body tissue D the chitinous exoskeleton cannot grow
D
complete metamorphosis
free-living larva transforms from a pupa into an adult.
crustaceans
lobster, crayfish, crab, shrimp;
Cnidaria have both _____. A stinging cells and a gastrovascular cavity B bilateral symmetry and radial symmetry C an exoskeleton and radial symmetry D an endoskeleton and bilateral symmetry
A
Compared to fruit flies, humans have _____. A a similar number of genes and similar types of genes that build the body parts and organs; however, the DNA sequences that regulate human gene expression are different B about 10 times as many protein-coding genes, which explains our much greater complexity C fewer protein-coding genes, but they are more flexible and can produce a greater diversity of proteins; this explains our great complexity relative to fruit flies D a totally different set of genes that program development of eyes, limbs, and other features in deuterostomes as opposed to protostomes
A
While dissecting an earthworm, you notice a closed tube that sits atop the digestive tract. Within each segment, this dorsal tube has a pair of branches that extend to connect with a similar ventral tube. What are you looking at? A a closed circulatory system B a nerve cord C an excretory system D an open circulatory system
A
You go to the supermarket and ask a clerk where you can find the gastropods. He takes you to the "weird food" section and points out a container of _____. A snails B squid C oysters D clams
A
Chordates are deuterostomes, and their closest relatives among the common phyla we have reviewed are _____. A Cnidaria B Echinodermata C Arthropoda D Annelida
B
Complete metamorphosis _____. A does not occur in beetles, flies, or bees B features a larval stage that looks different from the adult stage, with a pupa in between C is a feature of the life history of a minority of insect species D features larval stages with antennae and compound eyes
B
Consider the following list of animals: giant squid, earthworm, fish, snail, tapeworm, coral, and sea star. The two that belong to the same phylum are the _____, and their phylum is _____. A coral and sea star ... Echinodermata B giant squid and snail ... Mollusca C earthworm and tapeworm ... Annelida D fish and giant squid ... Chordata
B
How do cnidarians differ from the other common animal phyla profiled in this chapter? A Cnidarians lack muscles and nerves. B Cnidarians have harpoon-like stinging cells called cnidocytes. C Cnidarians have a gastrovascular cavity; other animals do not. D Cnidarians are bilaterally symmetrical.
B
Zoologists place chordates and echinoderms on one major branch of the animal phylogenetic tree, and molluscs, annelids, arthropods, and many other phyla on other major branches. Which of the following is a basis for this separation? A. whether the animals have a body cavity B. how the body cavity is formed C. whether the animals have skeletons D. what type of symmetry they exhibit
B
Digestion in sponges takes place in the _____. A choanocytes B spongin C amoebocytes D gastrovascular cavity
C
Jellies (also incorrectly called "jellyfish") and coral animals both _____. A have a complete digestive tract with a mouth and anus B have three tissue layers C have special stinging cells on their tentacles D consume algae
C
Which field of research investigates how developmental patterns evolve and give rise to new features in animals? A developmental biology B biogeography C evo-devo D animal ontogeny
C
Which option correctly describes a nematode? A. soft-bodied worm with a gastrovascular cavity B segmented worm with a cuticle and a complete digestive tract C worm with a cuticle, fluid-filled body cavity, and a complete digestive tract D segmented worm with a cuticle and gastrovascular cavity
C
Which phyla both possess a gastrovascular cavity that has only one opening? A Cnidaria and Nematoda B Platyhelminthes and Nematoda C Cnidaria and Platyhelminthes D Porifera and Cnidaria
C
You are given an unknown animal to study in the laboratory. It is long and ribbonlike and appears to be segmented. You find it has three tissue layers, it does not have a digestive tract, and it has male and female reproductive structures in the same individual. This animal probably is a(n) _____. A mollusc B cnidarian C tapeworm D annelid
C
In the ocean, you find an organism with a hard exoskeleton and jointed legs. It is _____. A an arthropod, more specifically an insect B an echinoderm, specifically a sea urchin C an arthropod, and can only be a horseshoe crab D an arthropod, and probably a crustacean
D
Sponges typically feed by _____. A. scraping bacteria and algae from hard substrates B. paralyzing small crustaceans with stinging cells C. absorbing nutrients from the guts of their hosts D. filtering small particles from water
D
The arthropods superficially resemble earthworms in that both groups have _____, yet the two are distinctly different because arthropods, but not earthworms, _____. A a distinct head and are bilaterally symmetrical ... have true organs B closed circulatory systems ... have bristles C a true coelom ... are protostomes D prominently segmented bodies ... have jointed appendages
D
Which feature of insects has promoted their diversification and evolutionary success? A Incomplete metamorphosis has contributed to the unusual success and diversity of insect groups that have this type of life cycle. B Insects have diversified so successfully because they possess repeated modular segments with similar or identical appendages on each of them. C Long adult life spans have helped promote the success of insects as a group. D Insects have repeated modular segments that develop independently of each other. Thus, insects have been able to evolve appendages that are specialized for diverse functions.
D
You are a researcher studying development in the chicken and identify a previously unknown gene that is expressed in the early embryonic cells that eventually differentiate to become liver cells. The gene plays a role in directing the development of this organ. Where else might you expect to find very similar homologous genes expressed? A virtually anywhere and at any time of development in any kind of organism, including plants and fungi B only in the same cell types, at the same stage of development, but in any kind of bird C only in the same cell types, at the same stage of development, in chickens and very closely related birds D in similar cell types at similar stages of development, in a wide diversity of animals; perhaps the gene will also play roles in the development of other structures
D
tunicate
adult tunicate has no trace of a notochord, nerve cord, or tail; stationary and attached; tunicate larva has all four distinctive chordates features; suspension feeders; molecular evidence suggests that these are the closest living non vertebrate relatives of vertebrates
A group of parasites called myxozoans have traditionally been considered simple multicellular protists. However, because these organisms possess stinging cells, some scientists consider them to be animals in the phylum that is named for such cells, the _____. flatworms roundworms sponges cnidarians
cnidarians
leeches
free living carnivores that eat snails and insects; sting contains anesthetic and anticoagulant (can dissolve blood clots);
Cephalaspids are an extinct group of vertebrates that possessed paired fins but no jaws. This group could be considered to be relatively advanced __________ that are ancestral to __________. hagfish; lampreys amphibians; reptiles lampreys; sharks and rays bony fish; lobe-finned fish
lampreys; sharks and rays
molluscs
phylum mollusca; soft bodied animals protected by hard shell; ex: snails, slugs, oysters, clams, squids; have separate sexes with reproductive organs situated in visceral mass; members of lophotrochozoan lineage; have a body cavity and complex organs and organ system; they have open circulatory system (pumps blood and distributes nutrients and oxygen throughout the body); 3 diverse types: gastropods, cephalopods; bivalvia
flatworms
phylum platyhelminthes; belong to lophotrochozoan lineage of bilaterians; bilateral symmetry and three tissue layers; lack body cavity; live in marine, freshwater and damp terrestrial habitats; have gastrovascular cavity that distributes food throughout the animal; one opening
Animal body plans vary in:
symmetry, presence of true tissues, number of embryonic layers, presence of a body cavity, and details of their embryonic development.
homeotic genes
transformation of a zygote into an adult animal is controlled by this; the master control genes that direct animal development
mitosis
zygote divides by mitosis
All animals can probably trace their lineage to a common ancestor that lived in the __________. A. Cretaceous (about 70 million years ago) B. mid to late Precambrian (1 billion years ago) C. Cambrian (542 million years ago) D. early Precambrian (over 2 billion years ago)
B
Among animals, sponges are unique in that they _____. A. are eukaryotes B. lack true tissues C. are multicellular D. ingest their food
B
The body cavity of a soft-bodied animal typically functions as a _____. A ventral surface B hydrostatic skeleton C digestive tract D location for food storage and digestion
B
Which of the following is associated with bilateral symmetry? A. no brain or clustered sensory organs B. a distinct head with a brain and sensory organs C. a lack of true tissues D. a stationary lifestyle
B
insects
make up nearly 75% of all animal species; can fly, waterproof coating on cuticle and have complex life cycle; 3 pair of legs;
meiosis
male and female animals make haploid gametes by meiosis; an egg and sperm fuse together making a zygote
earthworms
many intern body structures are repeated with segments; nervous system includes a simple brain and ventral nerve cord; digestive tract not segmented; closed circulatory system; hermaphrodites- contain both male and female reproductive structures; ingest soil and extract nutrients, aerating soil and improving its texture.
radula
many molluscs have this; this is used to scrape up food
insect life cycle
metamorphosis; more than 80% of insects goes though complete metamorphosis; the larval stage is specialized for eating and growing; the insect then emerges as an adult to reproduce;
A spectacular marine animal has a network of glassy spicules that forms a cagelike structure. This animal does not have true tissues. It is a suspension feeder. What cells or structures does this cage-building animal use to get nutrients from its feeding cells to other parts of its body? A. cnidocytes B. amoebocytes C. a gastrovascular cavity that provides circulation D. polyps
B
millipedes and centipedes
millipedes have two pairs of short legs per body segment, eat decaying plant matter; centipede have single pair of legs per segment, carnivore- eat flies, cockroaches
gastropod
"Stomach foot"; snails and slugs; found in fresh water, salt water and terrestrial environments; only molluscs that live on land; protected by single spiraled shell in which the animal can retreat when threatened;
cephalopods
"head foot"; predators; octopus, squid; use beak like jaws and a radula to crush their prey apart; have large brains and sophisticated sense organs;
polychaetes
"many hair"; marine; sandworms; have stiff bristles on appendages that helps the worm wriggle around;search for prey on the seafloor or live in tubes and filter food particles.
bastula
- an early embryonic stage - usually a hollow ball of cells - one side of bastula folds in and cells become rearranged to form a gastrula that establishes 3 embryonic layers
animals vs fungi in eating food
-fungi absorb nutrients after digesting food outside their body -animals digest food within their body after ingesting other organisms (dead or alive )
animal cells
-lack cell walls that provide strong support in bodies of plants and fungi -held together by extracellular structural proteins (abundant protein is collagen) and by unique types of intercellular junctions -almost all have muscle cells for movement and nerve cells for conducting impulses
metamorphosis
-major change of body form -larva goes through this and becomes an adult capable of reproducing sexually
animal reproduction and development
-most animals are diploid and reproduce sexually -eggs and sperm are the only haploid cells
chordates features that they share with invertebrate ancestors
1) dorsal, hollow nerve cord 2) notochord (a flexible supportive rod located between the digestive tract and the nerve cord); 3) pharyngeal slits located in the pharynx; 4) a muscular post anal tail; tunicate and lancelet = invertebrate chordates; although not unique, body segmentation is a characteristic of chordata;
A researcher finds an animal from a previously unrecognized group. Shee dissects it and finds that it clearly has a true coelom. What additional properties could she check next to further categorize this animal? A. She should determine the mechanism by which the mouth forms by examining a series of early embryos. B. She needs to decide if the organism has true tissues. C. She should determine if there are two or three tissue layers. D. She needs to check whether the organism has a body cavity.
A
If an organism is a protostome, what else can you conclude about its body plan? A. It is bilaterally symmetrical and has three tissue layers. B. The opening formed during gastrulation ultimately becomes the anus. C. It is radially symmetrical. D. It has two tissue layers.
A
Our most current understanding of animal phylogeny is based on __________. A. molecular data B. morphology or body plan C. ecological niches of the animal groups D. fossil record
A
Which of the following is radially symmetrical? A. a doughnut B. a spoon C. a submarine sandwich (a.k.a. hoagie, sub, grinder, or bomber) D. an automobile
A
A graduate student finds an organism in a pond and thinks it is a freshwater sponge. A professor thinks it looks more like an aquatic fungus. How can they decide whether it is an animal or a fungus? A. Look for cell walls under a microscope. B. See if it reproduces sexually. C. See if it is a eukaryote or a prokaryote. D. Figure out whether it is autotrophic or heterotrophic.
A Fungal cells have cell walls, and animal cells do not.
A researcher discovers a mysterious unknown multicellular eukaryotic organism. She would be confident that it is an animal if she observed that it __________. A. has muscles and nerve cells B. requires organic matter as a source of energy and carbon C. is an autotroph D. has rigid cell walls
A Muscles and nerves are typical of many animals but are not found in any other multicellular eukaryotes. Their presence would strongly indicate that the mystery organism is an animal.
The difference between pseudocoelomates and animals with a true coelom is that pseudocoelomates _____ whereas coelomates _____. A are protostomes ... are deuterostomes B do not have a body cavity ... have a body cavity C have a body cavity partially lined with tissue derived from mesoderm ... have a body cavity completely lined with tissue derived from mesoderm D exhibit radial symmetry ... exhibit bilateral symmetry
C
The phrase "Cambrian explosion" refers to _____. A. the evolutionarily sudden proliferation of dinosaur species B. the origin of the first soft-bodied animals C. the rapid adaptive radiation of marine animals that gave rise to most extant animal phyla D. the asteroid impact that caused the mass extinction at the K-T boundary
C
The presence of a coelom or other form of body cavity is advantageous because it _____. A allows for a third embryonic germ layer B permits the development of bilateral symmetry C allows room for the development and movement of internal organs D is necessary for a complete digestive tract
C
Which combination of features would occur in a typical animal? A. unicellular, heterotrophic, obtain food by ingestion B. multicellular, heterotrophic, obtain food by absorption, have cell walls composed of chitin C. multicellular, heterotrophic, obtain food by ingestion, lack cell walls D. multicellular, autotrophic, have cellulose-reinforced cell walls
C
Which lists the three tissue layers in a typical animal in the correct order, starting from inside the digestive tract? A. zygote → blastula → gastrula B. endoderm → ectoderm → mesoderm C. endoderm → mesoderm → ectoderm D. ectoderm → endoderm → mesoderm
C
Animals of one common phylum are NOT bilaterians but are eumetazoans. What phylum is it? A. Chordata B. Annelida C. Porifera D. Cnidaria
D
Suppose you could travel back to the Cambrian period in a time machine and carry a full laboratory along with you. To better understand the Cambrian explosion, you might want to _____. A. see if animals had gastrula stages B. look for multicellular aggregates of choanoflagellates that were forming the first animals C. measure carbon dioxide levels in the atmosphere and bring traps to collect terrestrial arthropods D. look for evidence of complex predator-prey relationships and measure oxygen levels in the atmosphere
D
The presence of a coelom or other form of body cavity is advantageous because it _____. A. allows for a third embryonic germ layer B. permits the development of bilateral symmetry C. is necessary for a complete digestive tract D. helps protect the suspended organs from injury
D A body cavity enables the internal organs to grow and move independently of the outer body wall while being protected from injury.
athropod appendage
adapted for sensory reception, defense, feeding, walking and swimming
invertebrate
animals without a back bone
nematodes body
are cylindrical with a blunt head and tapered tail; several layers of touch non living material called a cuticle covers the body and prevents it from drying out; cuticle also protects them from the host's digestive system;
open circulatory system
blood is pumped through vessels that open into body cavities where organs are bathed in blood
closed circulatory system
blood remains enclosed in vessels as it distributes nutrients and oxygen throughout the body
Biologists make hypotheses about the phylogeny of animal groups using evidence from:
body plan characteristics, the fossil record, and most recently, molecular data, chiefly DNA sequences.
The extraordinary success of insects is due to:
body segmentation, an exoskeleton, jointed appendages, flight, a waterproof cuticle, and a complex life cycle with short generations and large numbers of offspring.
bivalvia
clams, oysters, mussels and scallops; shells divided into two halves that are joined together; suspended feeders; mantle cavity contains gills that are used for feeding and gas exchange; sedentary (living in sand or mud);
gastrovascular cavity in cnidarians
cnidarians mouth leads to this; which functions in digestion, in circulation, and as a hydrostatic skeleton; one opening
athropods
crayfish, lobsters, crabs, spiders, insects, ticks; diversity and success related to their segmentation, hard skeleton, and jointed appendages; ecdysozoan lineage; body and appendage covered with exoskeleton (an external skeleton that protects the animal); cuticle hardened by layers of protein and chitin; arthropod must shed its old exoskeleton to grow; this process called molting, or ecdysis; open circulatory system; four major lineages: insects, chelicerates, crustaceans, millipedes and centipedes
bilateral symmetry
distinct left and right sides;
cambrian period
diversification appears to have been accelerated during this period (535 - 525 million years ago); many fossils found in british columbia;cambrian animals had hard body parts such as shells and spikes; scientists classified more than third of the fossils of burgess shale (sedimentary rock) to arthropods;
insects modular body plan
each embryonic segment is a separate building block that develops independently of the other segments; a mutation that changes homeotic gene expression can change the structure of one segment without affecting other segments
ingestion
eating food
sponges as suspended feeders
feed by collecting food particles suspended in water that streams through their bodies; choanocytes trap food particles in mucus on the collars and then engulf it by phagocytosis ; amoebocytes pick up food from choanocytes, digest it and pass it to other cells
protostomes
first opening of embryo is mouth
the lineage that gave rise to animals have diverged from what ancestor more than 1 billion years ago? (thought to)
flagellated unikont
mesoderm
forms the muscles and most internal organs
list characteristics arthropods have in common.
hard skeleton; specialized joint appendages; segmentation
nemotodes digestion
have a complete digestive tract, extending as a tube from mouth to anus; food travels from one way through the system and is processed as it moves along; advantage is that different part of the tract can be specialized in different functions;
body cavity (coelom)
helps protect organs from injury
chelicerates
horseshoe crab; scorpions, spiders, ticks and mites collectively called arachnids; most arachnids live on land.
larva
immature individual that looks different from the adult animal
Much of the diversity in body form among the animal phyla is associated with variations in what?
in where and when homeotic genes are expressed within developing embryos.
first hypothesis of why the arthropod body plan is successful
increase in the number of homeotic genes led to the diversity of segment and appendage types in arthropods (proved false because velvet worms had same set of arthropod homeotic genes - conclusion: body segments did not arise from new homeotic genes )
distinctions between body plans help scientists do what?
infer the phylogenetic relationships between animal groups
3 main body parts of molluscs
muscular foot (functions in locomotion); visceral mass (contains most of the internal organs) and mantle (a fold of tissue that drapes over the visceral mass and secretes a shell) - mantle extends beyond the visceral mass producing a water filled chamber called mantle cavity (houses the gills)
radial symmetry
no matter where you cut it, both halves are the same; no distinct right or left side
tapeworms
parasitic group of flatworms; inhabit the digestive tract of vertebrates; long ribbon like body with repeated units; absorb nutrients across their body surface and have no digestive tract; have units at the posterior end that are full of ripe eggs that pass out of the host's body through feces
annelids
phylum annelida; segmened body; lophotrochozoans lineage; segmentation played a key role in the evolution of many complex animals; segments = great flexibility and mobility; found in damp soil, in sea and in most freshwater; three main groups: earthworms, leeches, polychaetes
sponges
phylum porifera; have no nerve or muscles; asymmetric; marine animals; a simple sponge resembles thick walled sac pierced with holes; waters come in through the holes to central cavity and then pours out through bigger holes;
free living flatworms
planarians; eyes and other sense organs contact the environment first; feeds through a mouth that is at the tip of muscular tube; live on the undersurface of rocks in freshwater ponds and streams; have heads with light-sensitive eyecups, flaps to detect chemicals, dense clusters of nerve cells that form a simple brain and a pair of nerve cords that run the length of the body, and a branched gastrovascular cavity with a single opening.
Invertebrates do what for humans
play critical roles in natural ecosystems and; provide valuable services to humans; Reef-building corals create enormous structures that provide support and shelter for hundreds of other species; Reef-dwelling cone snails produce a powerful painkiller in their venom; Freshwater mussels filter and improve water quality in natural ecosystems and reduce the cost of water treatment for human uses.
cindarians exhibit two kinds of body forms:
polyp (hydras, sea anemones- cylindrical body with tentacles extending from one end) and medusa (jellyfish); some cnidarians pass from one body form to another (polyp -> medusae) while others only stay at one form
cnidarians
radial symmetry; two tissue layers; have outer epidermis and an inner cell layer that lines the digestive cavity; carnivores (use their tentacles to eat small animals and protists); named after their stinging cells (cnidocytes) used to kill animals and in defense;
what ignited the cambrian explosion?
scientists hypothesize it happened due to increase in oxygen and increase in complex predator - prey relationship; highly probable that set of homeotic genes (genetic framework for complex bodies) was already in place;
deuterostomes
second opening of embryo is mouth
One phylogenetic tree recently revised to reflect new information distinguishes between:
sponges ( lack true tissues) and eumetazoans (true animals); eumetazoans split into two lineages: cnidaria and and all other (cnidaria has radial symmetry and 2 layers formed in gastrulation while all the rest have bilateral symmetry with 3 layers formed- bilaterians; protostomes (ecdysozoans and lophotrochozoans) and deuterostomes (echinodermata and chordata);
lancelets
suspension feeders; exhibit the four distinctive chordate features; represent earliest branch of chordate lineage;
incomplete metamorphosis
transition from larva to adult is achieved through multiple molts, but without forming a pupa.
body of sponges
two layers of cell; inner cell layer called choanocytes (contains flagellated cells that help to sweep water through the sponge's body); amoebocytes produce supportive skeletal fibers (composed of flexible protein called spongin and mineralized particles called spicules);
