21 - Animal Evolution and Diversity

how do you differentiate the different mutlicellular kingdoms?

plants - autotrophs

fungi - absorptive heterotrophs

animals - ingestive heterotrophs

What structures support animal cells?

collagen, different to cell walls in plant cells

How are nervous and muscle tissue unique?

They define the characteristics of animals

what are tissues composed of?

An integrated group of cells with a common structure, function, or both

What four tissue types do complex animals have?

1. epithelial

2. connective

3. muscle

4. nervous

What is the benefit of a complex body plan?

it helps animals living in variable environments to maintain a relatively stable internal environment.

How is animal reproduction characterized?

• most reproduction is done sexually

• diploid stage usually dominates life cycle

how does animal reproduction differ from plants?

sperm and egg cells are produced directly by meiotic division (plants have alternation of generations and produce gametophytes)

What is cleavage

A process that animal zygotes undergo where the cells divide without any growth

What does cleavage lead to?

formation of a blastula - often in the form of a hollow ball of cells

What happens after the blastula forms?

it will undergo gastrulation, forming a gastrula w/ diff layers of embryonic tissues

What types of body plan symmetry are used to classify animals?

• radial symmetry (no front and back, or left and right)

• bilateral symmetry (only one imaginary cut divides the animal into mirror- image halves)

Describe the steps of embryonic development

1. animals reproduce sexually

2. after spern fertilizes egg, the zygote (2n) undergoes rapid cell division (cleavage)

3. blastula undergoes gastrulation

what are the different types of embryo cleavage?

• protostome (cleavage spirally, determinate)

• deuterostome (cleavage radially, indeterminate)

What are tissues?

collections of specialized cells isolated from other tissues by membranous layers

What are the three germ layers that give rise to tissues and organs of animal embryos

1. ectoderm

2. endoderm

3. mesoderm

What are the different embryonic layers?

1. sponges (porifera) lack true tissue

2. diploblastic - animals with ectoderm and endoderm (includes cnidarians and a few other groups)

3. triploblastic - animals have an intervening mesoderm layer; these include all bilaterians (includes flatworms, arthropods, vertebrates, and others)

What are the different ways in which the coelom (body cavity) forms?

• in protostome, the mesoderm splits to form the coelem

• in deuterostome, the mesoderm buds from the wall of the archenteron from the coelom

• in coelomates, animals possess a true coelom

• in hemocoelomates, animals contain a true pseudocoelom

• in acoelomates, animals lack a coelom

What happens to the blastospore?

• in protostome, it becomes the mouth

• in deuterostome, it becomes the anus

What does morphological and molecular data suggest about animal evolution?

it shows that the common ancestor may have resembled modern choanoflagellates (protists that are closest living relatives of animals)

What are some characteristics of porifera?

• lack true tissues and organs

• sedentary and live in marine or fresh waters

• suspension feeders, captures food through particles suspended in the water passing through their body

• most similar to choanoflagellates

What are the different components of porifera anatomy?

• choanocytes: flagella circulates water and captures food

• amoebocyte: transports nutrients and produces skeletal fibers (spicules)

• porocytes: span the body wall to make pores

• osculum: a large opening for water

What are eumetazoa (“true animals”

• a clade of animals with true tissues

• phyla ctenophora and cnidaria branch off first

What are some shared characteristics of the eumetazoa?

• radially symmetrical

• diploblastic

What are the different animals under phylum cnidaria?

• jellies, corals, hydras

• carnivores (tentacles contain cnidocytes)

what is the body plan of phylum cnidaria?

• diploblastic

• radial symmetry

• muscles and simple neural net

• sac w a central gastrovascular cavity

• single opening mouth and anus

• sessile polyp or motile medusa stage during life cycle

What clade do most animal phyla fall under?

Bilateria

• animals called bilaterians

What are the three major clades of bilaterian animals?

• ecdysozoa

• lophotrochozoa

• deuterostomia

What did the Cambrian explosion do?

• produced most of the bilaterian fossils

What are ecdysozoa?

• invertebrates that shed their exoskeletons through ecdysis

• protostomes

• phyla arthropada and nematoda

• hard exoskeleton (chitin)

• segmented body, jointed appendages for movement

lophotrochozoans

• contain animal phyla mollusca and annelida (think earth worms)

• feeding structure called lophophore

• others have distinct developmental stage called trochophore larva

deuterostomia

the only group to contain both invertebrates and vertebrates

What four key characteristics distinguish chordates

• notochord

• dorsal, hollow nerve cord

• pharyngeal slits or clefts

• muscular, post anal tail

what are the 5 important points about the relationships among living animals that are reflected in their phylogeny?

1. animals share a common ancestor (monophyletic)

2. sponges are basal animals

3. eumetazoa is a clade of animals w true tissues

4. most animal phyla belong to the clade bilateria

5. the three major clades of bilaterian animals are all ivertebrates (lack a backbone), except chordata

What key characteristics of animals make them such efficient consumerS?

• animals are heterotrophic (obtain energy through eating other organisms)

• tissues formed from layers of embryonic cells

• process food inside bodies (digestive system)

• nerve and muscle cells

• can move and detect + capture potential prey