Chapter 29: Animals

characteristics of all animals

-multicellularity

-heterotrophic metabolism

-internal digestion

-movement and nervous system

are all animals monophyletic

yes

morphological synapomorphies of animals

-extracellular matrix

-unique cell junction

-similarity in developmental genes

extracellular matrix

contains collagen and preoteoglycans

cell junctions in animals

tight junctions, desmosomes, and gap junctions

hox genes

developmental genes that are highly conserved

common ancestor of animals

colonial flagellated protist, similar to choanoflagellates

choanoflgellates are similar to…

multicellular sponges

why did colonies form

to make prey capture easier

body plan

general construction of organ systems

five key features of body plan

-body symmetry

-body cavity

-segmentation

-external appendages

-development of nervous system

symmetry

animal can be divided into similar halves on at least one plane

asymmetric animals

placozoans and most sponges

radial symmetry

one main axis around which body parts are arraged

animals with radial symmetry

cnetophores and cnidarians

cnetophores

comb jellies

cnidarians

jellyfish

bilateral symmetry

animals that move in one direction and can be divided into mirror image halves on only one plane

bilateral symmetry planes

-anterior or posterior

-dorsal and ventral

anterior

head

posterior

tail

dorsal

back

ventral

belly

bilateral symmetry is correlated with…

cephalization

cephalization

-concentration of sensory organs and nervous tissues at the anterior

-anterior encounters environment first so this is an evolutionary advantage

body cavity

structure of the internal, fluid filled body cavity influences animal movement

acoelomate

-no fluid filled body cavity

-space between gut and body wall is filled with cells called mesenchyme

how do acoelomates move

cilia

acoelomate exmaple

flatworm

pseudocoelomate

body cavity is pseudocoel, a fluid filled space in which organs are suspended, with muscles on the outside

pseudocoelomate example

roundworm

coelomate

body cavity is a coelom that develops within the mesoderm

peritoneum

tissuse that covers organs in the coelomate

coelomate example

earthworm

segmentation

-facilitates separation of body regions

-allows animals to alter body shape and control movements precisely

appendages

locomotion is important fo finding food, mates, and avoiding predators

echinoderms

have tube feet to move across a substrate

limbs

highly specialized for rapid, controlled movements

anthropods and vertebrates

have jointed limbs

animals with wings for limbs

birds, bats, insects, and pterosaurs

appendage functions

-antennae for sensing environment

-claws and mouths for capturing prey and chewing food

-reproduction, such as sperm transfer or egg incubation

animals without nervous system

placozoans and sponges

nerve nets

diffuse systems in cnetophores and cnidarians

central nervous system

-in bilaterians

-coordinates muscle action, movements of body parts, and processes sensroy info

animal feeding

are animals are heterotrophs

some animals have…

photosynthetic endosymbiants, but most must expend energy to obtain food from the environment

motile animals

can move through environments to where food is located

sessile animals

stay in one place and must move food to themselves

filter feeders

use straining devices to filter small organisms and organic molecules from air and water

sessile filter feeders

-rely on water currents to bring food

-expand energy to move water past their straining device

motile filter feeders

move body to food source

motile filter feeder examples

flamingoes and baleen whales

herbivores

eat plants or part of plants, the plant is not usually killed

many herbivores feed on…

a single plant

why do herbivores have long digestive tracts

land plants have tissues that are difficult to digest and defensvie chemicals that must be detoxified

predators

-capture and subdue other animals

-have structures like sharp teeth, claws, and well developed sensory organs to detect prey

-stalk prey or wait for it to come

omnivores

-eat both plants and animals

-may change diet during different life stages

omnivore examples

humans and raccoons

parasites

-live in or on another animal, the host

-consume parts of the host or hijack its nutrients

-usually smaller than the host with complex life cycles

parasite that consumes host

tick

parasite that hijacks nutrients

tapeworm

is the host usually killed

no

endoparasite

-live inside host and have no digestive system

-absorb food directly from host

endoparasite example

flatworms

ectoparasite

-live on the outside of the host and often have mouthparts to pierce or suck host’s fluids

ectoparasite example

fleas, ticks, and mosquitoes

detritivores

feed on dead bodies and decomposing organic matter

detritivores synonym

decomposers

detritivore function

return nutrients to environment

detritvore example

earthworms, millipedes, insects, crustaceans

sessile marine animals

-discharge sperm and egg into water for fertilization

-feed on plankton

-travel long distances before settling

marine sessile larvae

trochophore and nauplius

trochophore

mollusks

nauplius

crustacean

cleavage

the first few divisions of a zygote, can take on many patterns

radial cleavage

-cells divide completely and evenly

-ancestral state for bilaterians

spiral cleavage

-a complex, derived form of radial cleavage

-lophotrochozoans

ecdyzosoans cleavage

has an idiosyncratic cleavage pattern that is neither radial or spiral

monoblastic

-no tissue types or embryonic layers

monoblastic example

sponges

diploblastic

animals have two cell layers, ectoderm and endoderm

triploblastic

has three cell layers; ecto endo and mesoderm

in early development, the embryo forms a

gastrula

gastrulation

-results from a hollow ball one cell thick, with an indent that becomes a blastophore

types of bilaterians

having bilateral symmetry

protostomes

-mouth first

-blastophore develops into mouth

deuterostomes

-mouth second

-blastophore develops into anus

-mouth develops later

bilaterian clade

monophyletic

synapomorphies of bilaterians

-strong bilateral symmetry

-3 cell layers in embryo

-central nervous system

nonbilaterian groups

ctenophores, sponges, placozoans, and cnidarians

nervous systems evolved

independently in ctenophores, cnidarians, and bilaterians

why did nervous systems evolve

-response to similar selection pressures

-associated with multicellularity, movement, and prey capture

-no longer considered homologous

first animals

were thought to have few cells and to have been quite small

in Cambrian…

-larger, more complex animals developed

-result of earth warming and increase O2 concentration

sponges

-8500 species

-some specialized cells but no distinct embryonic layers or true organs

spicules

-skeletal elements on sponges

glass sponges and demosponges

have spicules made of silicon dioxide

calcareous sponges

have spicules made of calcium carbonate

sponge feeding

most are marine filter feeders

sponge body plan

an aggregattion of cells around a water canal system