Chapter 18-19 Flashcards
what are animals
multicellular, heterotrophic eukaryotes that obtain nutrients by ingestion.
animal cells
- distinctive structures and specializations
- lack cell walls
- held together by extracellular structural proteins
lineage that gave rise to animals
-diverged from flagellated unikont ancestor about 770 million years ago
when did animal diversification accelerate?
535-525 million years ago during the Cambrian period. Cambrian explosion.
vertebrates
- only 1 phylum
- animals with a backbone
invertebrates
- around 96% of all animals
- animals that lack a backbone
Animal body plans vary in
- symmetry
- presence of true tissues
- number of embryonic layers
- presence of a body cavity
- details of their embryonic development
eumetazoa clade
“true animals.” animals with tissues
bilateria clade
branch of eumetazoa. animals with bilateral symmetry
-three main lineages: Lophotrochozoa, Ecdysozoa, Deuterostomia
Lophotrochozoa
flatworms, molluscs, annelids
Ecdysozoa
nematodes and arthropods
-have external skeletons that must be shed for the animal to grow
Deuterostomia
echinoderms and chordates
sponges
- are simple animals
- do not have true tissues
- usually lack body symmetry
- are usually marine, although some are found in fresh water.
choanocytes
flagellated “collar” cells that make up the inner cell layer in sponges that help to sweep water through the sponge’s body.
suspension feeders
animals that collect food particles from water passed through some type of food-trapping equipment
-sponges
cnidarians
- branch of eumetazoans
- hydras, sea anemones, corals, and jellies
- characterized by raidal symmetry and bodies arising from only 2 tissue layers.
polyp
- body form of cnidarians
- hydras and sea anemones have cylindrical body with tentacles projecting rom one end
medusa
- body form of cnidarians
- marine jelly
- move freely about in the water
cnidocytes
stinging cells of Phylum Cnidaria.
-function in defense and in capturing prey
flatworms/phylum platyhelminthes
- belong to lophotrochozoan
- bilateral symmetry and three tissue layers
- three main groups: free-living flatworms, flukes, tapeworms
flukes
live as parasites in other animals
tape worms
parasitic group of flatworms. inhabit the digestive tracts of vertebrates
roundworms/nematodes
- bilateral symmetry
- three tissue layers
- have a fluid-filled body cavity
- a digestive tract with 2 openings
molluscs
snails, slugs, oysters, clams, octopuses, and squids
- soft-bodied animals, but most protected by a hard shell
- a muscular foot, which functions in locomotion,
- a visceral mass containing most of the internal organs,
- a mantle, which may secrete a shell that encloses the visceral mass
- a circulatory system.
gastropods
largest group of molluscs
- only molluscs that live on land
- protected by a single, spiral shell into which the animal can retreat when threatened
bivalves
group of molluscs
- clams, oysters, mussels, and scallops
- shells divided into two halves that are hinged together
- most suspension feeders
cephalopods
group of molluscs
-adapted to lifestyle of fast, agile predators
segmentation
the subdivision of the body along the length into a series of repeated parts
annelids
segmented worms
- clades errantians and sedentarians
- segmentation, the subdivision of the body along its length into -a series of repeated parts,
- a nervous system, and
- a closed circulatory system in which blood remains enclosed in vessels throughout the body.
erratians
- clade of annelids
- marine and may have an active, mobile lifestyle
sedentarians
- clade of annelids
- less mobile than errantia
- include earthworms, many tube-dwellers, and leeches
arthropods
- crayfish, lobsters, crabs, barnacles, spiders, ticks, and insects
- have jointed appendages and an exoskeleton
chelicerates
group of arthropods
- bodies consist of cephalothorax and an abdomen, and lack atennae
- most are arachnids
arachnids
scorpions, spiders, ticks, and mites
myriapods
group of arthropods
-millipedes and centipedes
pancrustaceans
group of arthropods
- crustaceans and insects. nearly all aquatic
- lobsters, crayfish, barnacles, crabs, and shrimps
echinoderms
sea stars, sand dollars, and sea urchins
- slow-moving or sessile marine animals
- an endoskeleton of hard calcium-containing plates under a thin skin,
- a water vascular system based on a network of water-filled canals that branch into extensions called tube feet
- the ability to regenerate lost arms.
chordata
- invertebrates
- possess a dorsal, hollow nerve cord, a notochord, pharyngeal slits, and post-anal tail.
- a dorsal, hollow nerve cord
- a flexible, supportive, longitudinal rod
- the notochord,
- pharyngeal slits
- a muscular post-anal tail.
Biologists make hypotheses about the phylogeny of animal groups using evidence from
- body plane characteristics
- the fossil record
- molecular data, chiefly DNA sequences.
Tunicates and lancelets
- do not have a backbone
- use their pharyngeal slits for suspension feeding.
Lancelets
small, bladelike chordates that live in marine sands.
tetrapods
- jawed vertebrates with limbs and feet that can support weight on land.
- first vertebrates on land
what completed the transition to land
amniotes, tetrapods with a terrestrially adapted egg
Hagfishes and lampreys
- have rudimentary vertebrae
- have a notochord for the body’s main support
- lack hinged jaws and paired fins.
hagfishes
deep-sea scavengers that produce slime as an antipredator defense.
lamprey
parasites that penetrate the sides of fishes with their rasping tongues.
jawed vertebrates
- appeared in the fossil record about 440 million years ago
- diversified, using their paired fins and tail to chase a wide variety of prey.
how did jaws possibly evolve
by modifications of skeletal supports of the anterior pharyngeal (gill) slits.
3 lineages of jawed vertebrates
gills and paired fins are commonly called fishes:
- chondrichthyans
- ray-finned fishes
- lobe-finned fishes
chondrichthyans
- sharks and rays
- have a flexible skeleton made primarily of cartilage
ray-finned fishes
- tuna, trout, andgoldfish
- have a skeleton made of bone
lobe-finned fishes,
- coelacanths and lungfishes
- have a series of rod-shaped bones in their muscular pectoral and pelvic fins.
when did tetrapods arise?
During the late Devonian, a line of lobe-finned fishes gave rise to tetrapods
-All subsequent groups of vertebrates, amphibians, mammals, and reptiles (including birds) are descendants of these early land-dwellers
amphibians
- include salamanders, frogs, and caecilians
- use their moist skins to supplement their lungs for gas exchange
- often have poison glands in their skins
- usually lay their eggs in water
- undergo metamorphosis from a larval stage to the adult form
- were the first tetrapods to colonize land.
amniotes
tetrapods with a terrestrially adapted egg
- reptiles, birds, mammals
- The major derived character of this clade is an amniotic egg
amniotic egg
- four internal membranes.
- The amnion is a fluid-filled sac surrounding the embryo.
- The yolk sac contains a rich store of nutrients for the developing embryo.
- The chorion (and allantois) enable the embryo to obtain oxygen from the air and dispose of carbon dioxide.
- The allantois also helps dispose of metabolic waste.
reptiles
- include lizards, snakes, turtles, crocodilians, birds, and extinct dinosaurs
- have a skin covered with scales and waterproofed with keratin
- obtain most of their oxygen using lungs
- are ectothermic
ectothermic
absorbing external heat rather than generating much of their own.
endothermic
using heat generated by metabolism to maintain a warm, steady body temperature.
what did birds evolved from
a lineage of small, two-legged dinosaurs called theropods.
oldest, most primitive known bird
Archaeopteryx, 150 million years old
mammals
- endothermic amniotes
- have hair, which insulates their bodies
- mammary glands, which produce milk.
- efficient respiratory and circulatory systems that support their high rate of metabolism
- teeth are differentiated for many kinds of diets.
monotremes
egg-laying mammals.
marsupials
have a brief gestation and give birth to tiny, embryonic offspring that complete development while attached to the mother’s nipples.
eutherians (placental mammals)
bear fully developed live young.
primates
-had evolved as small arboreal mammals by 65 million years ago
-characters include
limber joints
-grasping hands and feet with flexible digits
-a short snout
-forward-pointing eyes that enhance depth perception.
primate 3 groups
- lemurs, lorises, and bush babies
- tarsiers
- anthropoids, including monkeys and apes.
when did anthropoids begin diverging from other primates
about 55 million years ago.
Paleoanthropology
the study of human origins and evolution
genus Homo
includes hominins with larger brains and evidence of tool use.
homo ergaster
had a larger brain than H. habilis.
H. erectus
with a larger brain than H. ergaster, was the first hominin to spread out of Africa.
homo neanderthalensis
had a brain even larger than ours and hunted big game with tools made from stone and wood.
oldest known fossils with the definitive characteristics of our own species
- were discovered in Ethiopia
- are 160,000 and 195,000 years old.
old world monkeys
- Many arboreal, but some grounddwelling
- Nostrils open downward
- Lack prehensiletail
new world monkeys
- All arboreal
- Nostrils open toside; far apart
- Many have a long, prehensile (grasping) tail
