Ch 31 Animals 2 Flashcards by Colton Juarez

• The sister group of the rest of animals
– animals characterized by choanocytes
– choanocytes: flagellate collar cells similar to the choanoflagellates

Sponges

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– asymmetrical sac with pores for water to enter
– central cavity (spongocoel)
– opening (osculum) for water to exit

Sponge body

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– loosely associated
– do not form true tissues
– lack nerves and muscles

Sponge cells

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Sponges are generally _____, but

larvae swim with flagella

Sessile

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• Characterized by
– radial symmetry
– two tissue layers
– cnidocytes: cells containing stinging threads (nematocysts)
• Gastrovascular cavity
– with single opening that functions
• No brain: nerve cells form like mouth and anus nondirectional nerve net
– sensory cells connect with contractile cells

Cnidaria

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• Sessile polyp stage
– mouth on top
• Free-swimming medusa (jellyfish) stage
• May include both sexual and asexual reproduction
• Not alternation of generations
– only haploid stage is unicellular gametes (egg and sperm)

Cnidarian Life Cycle

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Classes of Cnidaria

Class Hydrozoa (hydras, Portuguese man-of-war)
Class Scyphozoa (jellyfish)
Class Cubozoa (“box jellyfish”)
Class Anthozoa (sea anemones, corals)

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– often without medusa stage

– solitary or colonial

Class Hydrozoa (hydras, Portuguese man-of-war)

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– medusa is dominant form

– among largest invertebrates

Class Scyphozoa (jellyfish)

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– have complex eyes

– actively hunt for prey

Class Cubozoa (“box jellyfish”)

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– polyps, no medusa
– may be solitary or colonial
– differ from hydrozoans in partitioned gastrovascular cavity

Class Anthozoa (sea anemones, corals)

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– fragile, luminescent marine predators
– like cnidarians, have radial symmetry and 2 tissue layers
– unlike cnidarians have separate mouth and anal pores
– eight rows of cilia that resemble combs
– tentacles with adhesive glue cells, don’t sting

Ctenophora: Comb jellies

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• More than 99% of animal species belong to Bilateria, the clade sharing a bilaterally symmetrical ancestor.

Bilateral Animals

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Bilateral Animal Adaptations:

– the coelom
– cephalization
– the central nervous system and true muscles

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• Body Cavity
• Starting point for many specializations of form
– Allows tube-within-a-tube body plan
• body wall is outer tube; inner tube is digestive tube
– Provides a space for complex internal organs
– An enclosed compartment of fluid under pressure
• Serve as hydrostatic skeleton: contracting muscles push against tube of fluid
• Allowing the diversity of animal movement types

Coelom

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• Evolution of a head
– concentration of sense organs and nerve cells at anterior end
– leading to central nervous system, including brain
• Increases effectiveness of bilateral animal
– to actively find food, shelter, mates
– to detect enemies

Cephalization

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• Characteristics
– mouth before anus
– spiral, determinate cleavage

Protostomes

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Protostomes Two groups
– Lophotrochozoa:
– Ecdysozoa:

From the merging of the trochozoans and the lophophorata

- Share the process of molting

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• Coelom apparently lost
– well-developed organs
• Gastrovascular cavity with only one opening
• Ladder-type nervous system
– 2 nerve cords that extend the length of body
• connections like rungs
– simple brain composed of two ganglia

Platyhelminthes (Flatworms)

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4 Classes of Platyhelminthes

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Class Turbellaria
Class Trematoda
Class Monogenea
Class Cestoda

– free-living flatworms, including planarians – marine & fresh water

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Class Turbellaria

– parasitic flukes

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Classes Trematoda and Monogenea

– parasitic tapeworms

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Class Cestoda

• Soft-bodied animals
– usually covered by a shell 
• Ventral foot
– for locomotion 
• Mantle
– covers visceral mass (body organs)

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Mollusks

• Most have open circulatory system (in hemocoel) – Cephalopods have closed circulatory system • Most have rasping radula for feeding – Bivalves are suspension feeders • Most marine mollusks have free- swimming, ciliated trochophore larva – part of the name: Lophotrochozoa – occurs in most Lophotrochozoans

Mollusks

4 classes of Mollusks

Class Polyplacophora Class Gastropoda Class Bivalvia Class Cephalopoda

* Includes marine chitons * Shells consist of 8 overlapping plates * Reduced head * No eyes

Mollusks: Class Polyplacophora

• Largest group of mollusks – snails, slugs, and their relatives • Body undergoes torsion – a twisting of the visceral mass

Mollusks: Class Gastropoda

• Suspension feeders: clams, scallops, oysters • Two-part shell – hinged dorsally (upper or back side) – encloses bodies

Mollusks: Class Bivalvia

``` • Includes squids, octopods, Nautilus • Active, predatory swimmers • Some of the most “intelligent” invertebrates • Tentacles surround the mouth – located in the large head ```

Mollusks: Class Cephalopoda

``` • Conspicuously long bodies • Segmentation – both internally and externally • Large, compartmentalized coelom – serves as hydrostatic skeleton ```

Annelids: Segmented Worms

3 classes of Annelids: Segmented Worms

Class Polychaeta Class Oligochaeta Class Hirudinea

``` • Marine worms with parapodia – appendages for locomotion, gas exchange • Parapodia have many setae – setae: bristle-like structures • Well-defined head with sense organs – unlike other annelids ```

Annelids: Class Polychaeta

• Earthworms • Characterized by few short setae per segment (not visible in this diagram) • Body divided into > 100 segments – separated internally by septa

Annelids: Class Oligochaeta

• Leeches – mostly fresh water • Characterized by absence of setae and parapodia • Have suckers – still sometimes used in medicine to remove excess fluid and blood accumulating near injuries

Annelids: Class Hirudinea

• Marine animals with a lophophore – ocean floor dwellers – lack distinct head • Lophophore – ciliated ring of tentacles surround the mouth – specialized to capture particles in water

Lophophorates

- Microscopic, multicellular - Have brain and eyepspots - Cell constant: mature individuals always have the same # of cells

Rotifers

``` • Ecdysis: molting; shedding cuticle • Highly successful • Probably not a monophyletic group – simplified body from multiple lineages – pseudocoelom: not surrounded by mesoderm • Body covered by tough cuticle – helps prevent desiccation • Decomposers, predators, parasites • aquatic and soil ```

Ecdysozoans: Nematodes (Roundworms)

• More than 80% of known animal species are arthropods. • Segmented animals with paired, jointed appendages • Armor-like exoskeleton of chitin – Molting necessary for arthropod to grow • Open circulatory system – Dorsal heart, pumps hemolymph • Aquatic forms have gills for gas exchange • Terrestrial forms have internal branching tubes (tracheae) or plate-like surfaces (book lungs) for gas exchange

Ecdysozoans: Arthropods

* Elongated with many segments * Uniramous (unbranched) appendages * Single pair of antennae

Myriapoda

2 classes of Myriapoda

– Chilopoda (centipedes) | – Diplopoda (millipedes)

* one pair of legs per segment | * predators with poison claws

– Chilopoda (centipedes)

* two pairs of legs per segment | * generally herbivorous

– Diplopoda (millipedes)

• Merostomes (horseshoe crabs) and Arachnids (spiders, mites, and relatives) • 2 part body with cephalothorax and abdomen • 6 pairs of uniramous, jointed appendages – 4 pairs serve as legs • First appendages are chelicerae – fang-like feeding appendages • Second are pedipalps • Some chelicerae and pedipalps are adapted for manipulation of food, locomotion, defense, copulation • No antennae, no mandibles

Chelicerates

``` • Lobsters, crabs, shrimp, pill bugs, barnacles • Body with cephalothorax and abdomen • Most have five pairs of walking legs • Appendages are biramous • Many have substantial specialization of appendages • Two pairs of antennae – sense taste and touch • Third appendages are mandibles – for chewing • Two pairs of maxillae – posterior to mandibles – manipulate and hold food ```

Crustaceans

Most successful animals in terms of number of species, number of individuals, and distribution – articulated: jointed, 3 part body – tracheated: having tracheal tubes for gas exchange – hexapod: having six uniramous appendages • many also with wings – malpighian tubules for excretion • efficient with water

Insects

• transition from one developmental form to another • some insects have no metamorphosis, only molting • others with incomplete metamorphosis – larva resembles adult without wings or reproductive structures • complete metamorphosis: -four distinct stages -larvae not like adult

Metamorphosis

``` • Versatile exoskeleton: protection • Segmentation: for mobility and specialization • Specialized jointed appendages – feeding, sensory, locomotion, etc. • Highly developed sense organs – tactile, auditory, visual, chemical • Ability to fly – contributes to wide distribution and survival • Diverse defense mechanisms – stingers, cryptic coloration • Sophisticated communication • Effective reproduction ```

Insect Adaptations

Ch 31 Animals 2 Flashcards

(48 cards)