topic 9: diversity of life -- invertebrates

animals are multicellular, heterotrophic eukaryotes that obtain their nutrients by _______

ingestion

TRUE OR FALSE: animals have cell walls

FALSE

what is a blastula?

a hollow ball of cells that is found in the early embryonic stage

what is gastrulation?

this is when the blastula folds inwards to form the gastrula

what is the gastrula composed of?

• endoderm

• ectoderm

• mesoderm

what is the endoderm?

this is the structure that ends up lining the digestive tract

what is the ectoderm?

this is the structure that ends up being the outer covering of the animal and central nervous system BASICALLY becomes the skin and spinal cord

what is the mesoderm?

this is the structure that ends up being the muscles and most internal organs

what is larva?

the immature version of an organism that looks different from its adult version

what is metamorphosis?

changing from a larva into an adult

what happened in the ediacaran period?

animals likely arose from a unikon ancestor and about 770 million years ago.

• these are “soft-bodied” animals

where was the oldest animal fossil discovered from ediacaran period?

ediacara hills of australia from 560myo

• these were “soft bodied” animals from 1cm-1m long

what happened in the cambrian period?

the RAPID diversification of animals

• animals developed hard body parts like shells, spikes, arthropods

what caused the cambrian explosion?

the variations in when and where homeotic genes were being expressed in developing embryos!

what is the phylum chordata?

a spinal cord is present

how many animal phyla are there?

about 35!

• 34 are invertebrates (no backbone)

• 1 is vertebrate (backbone)

what is radial symmetry?

when the body parts spread from the centre

• THINK anemone

what is bilateral symmetry?

when the right and left side are mirrored

what is the anterior end?

the head

what is the posterior end?

the tail end

what is the dorsal surface?

the back

what is the ventral surface

the bottom

what is tissue?

this is group of cells that have a common function and structure

what are protostomes?

when the first opening is the mouth

what are deuterostomes?

when the first opening is the anus

what are the 9 major animal phyla?

• sponges

• cnidarians

• platyhelminthes

• nematoda

• mollusca

• annelida

• arthropods

• echinoderms

• chordata

what are sponges?

these are the most simplest animals since they DON’T HAVE nerves or muscles

• some are radially symmetric, but most lack symmetry

where can we find sponges?

most are marine, but some can be found in freshwater

explain sponge structure

• sponges look like sacs with holes

  • the water enters through pores into a central cavity and then flows out. more complex has branching water canals

• composed of two layers of cells that are separated by a gelatinous layer

  • choanocytes and amoebocytes

what are choanocytes in sponges?

this is the inner layer of cells in a sponge that helps to sweep water through the body

• basically cilia that sweep into mouth

what are amoebocytes in sponges?

this is the outer layer of cells in a sponge. they produce skeletal fibres that help provide support

what are the skeletal fibers in sponges composed of?

spongin proteins and spicule particles

what are suspension feeders in sponges?

these collect food from water that’s being passed through

• choanocytes trap food and eat them via phagocytosis

• then the amoebocytes will get the food, digest it, bring it to other cells

what does sessile mean?

anchored in place

are sponges sessile?

yes! in addition to being sessile, they also have toxins and antibiotic like substances as their form of defense against pathogens, parasites and predators

what are cnidarians?

these include hydras, sea anemones, corals, and jellies.

• they have radial symmetry

what is polyp form with cnidarians?

when the cnidarian is a cylindrical body with tentacles projecting from one end. they are also often STATIONARY

• ex: sea anemones

what is the medusa form with cnidarians?

when they’re umbrella-shaped with a fringe of tentacles around the lower edge. they move FREELY in the water

• ex: jellyfish

TRUE OR FALSE: some cnidarians have both polyp and medusa form

TRUE! others can be either or

explain cnidarian composition and tissues

• there are 2 tissue layers

  • outer epidermis, and the inner cell layer that lines the digestive cavity

  • there is also a jelly filled middle region that may contain some amoeboid cells

• tentacles help to capture small organisms into the mouth

  • polyp: on top

  • medusa: centre of underside

how do cnidarians eat?

• their tentacles push small organisms into their mouth

• the mouth leads to a gastrovascular cavity where the food will be digested

  • in that cavity is a fluid that circulates the nutrients and oxygen to all cells. also removes waste

  • if the mouth is CLOSED, the muscle cels contract to shorten or lengthen the body to produce movement

what happens to undigested food and other wastes in cnidarians?

the leave through the mouth

what makes corals different from other cnidarians?

they secrete a hard external skeleton to make “rocks”

what are cnidocytes?

these are stinging cells

what is the function of cnidocytes?

defense and capture of prey

what is the structure of cnidocytes?

fine thread coiled in a capsule. this thread can then sting or entangle prey

what are cubozoans?

a group cnidarians that have highly toxic cnidocytes

• ex: sea wasps

what are platyhelminthes?

AKA flatworms

• simplest bilateral symmetry organisms

what clade do platyhelminthes belong to?

lophotrochozoan

what is the structure of platyhelminthes?

• composed of 3 tissues

• lack a body cavity

  • however, has a gastrovascular cavity with ONE opening. branches out to distribute food throughout animal

• from 1mm to 20m

• they can be free living and parasitic

where can we find platyhelminthes?

marine, freshwater, damp terrestrial habitats

what are the three major groups of platyhelminthes?

planarians, flukes and tapeworms

what are planarians?

these are free living flatworms → 5-10mm

where can we planarians?

the undersurface of rocks in freshwater ponds/streams

what is the structure of planarians?

• have a head with light sensitive eyecups and flaps that detect chemicals

• have a dense cluster of nerve cells for a brain

• have nerve cords that connect small nerves that branch throughout the body

• brain, sense organs and mouth are all at the anterior end

  • mouth at belly

what are flukes?

these are parasites in OTHER ANIMALS. they do this by SUCKING onto hosts.

what is the composition of flukes?

• they have a tough protective covering

  • interior of worm contains reproductive organs

what is the lifecycle of flukes?

• larvae develop INSIDE an intermediate host

• larvae then infect the final host, where they will live as adults

• ex: schistosomes → first in snails, then humans

what are tapeworms?

long ribbon-like parasites

where can we find tapeworms?

in the digestive tract of vertebrates

what is a scolex in tapeworms?

• the anterior end of the tapeworm

• contains hooks and suckers to grip onto host’s intestinal wall

do tapeworms have a mouth? an anus?

no and no. only have suckers and hooks to help it from being flushed out while absorbing nutrients

how does a tapeworm get its nutrients?

since it’s so thin, it doesn’t need a digestive tract and just absorbs nutrients from host so that it can reach all of its cells

what is the main composition of tapeworms?

male and female reproductive structures

what is at the posterior end of tapeworms?

ripe eggs that will break off and pass out of host via their feces

what is the tapeworm lifecycle?

• prey species are infected by eating egg contaminated grass

• larval tapeworms develop in host

• predator then becomes infected when it eats contaminated prey

• adult tapeworm develops in predator

what are the main ways humans can contact tapeworms?

UNDERCOOKED beef, pork, fish that are infected with microscopic larvae

what are nematoda?

AKA nematodes or roundworms

• bilaterally symmetric

what is the composition of nematodes?

• embryo has 3 tissue layers with a fluid filled cavity

• its digestive tract has two openings

  • anterior end and posterior end

• cylindrical shape with a blunt head and tapered tail

• 1mm-more than 1m

what is the anterior end in nematoda?

it churns food with enzymes

what is the posterior end of nematoda?

absorbs nutrients and disposes of waste

what is the cuticle in nematodes

several layers of tough nonliving material that covers its body

• helps to maintain hydration and protects worm from the host’s digestive system

  • THINK: like human skin is tough for protection

what happens to the cuticle when the nematode is growing?

it doesn’t grow with the nematode, it sheds then secretes a larger one

what is the function of the body cavity in nematodes?

since nematodes don’t have a true circulatory system, all of the nutrients that it absorbs @ digestive tract will be spread throughout its body

how do the longitudinal muscles of a nematode move?

whip-like

where can we find FREE-living nematodes?

everywhere where there is rotting ORGANIC matter since they’re important decomposers in soil @ bottom of lakes and oceans

TRUE OR FALSE: some free living nematodes are predators that eat microscope

TRUE! caenorhabditis elegans is an example

where can we find PARASITIC nematodes?

in moist plant tissues and animal body fluids and tissues

what is the LARGEST parasitic nematode?

parasites of whales that are 7m long

humans are hosts to how many parasitic nematodes?

50 species

how does dog heartworm work?

via mosquitos: they pick eggs from an infected host and then transmit it to another animal

• mosquitos are vectors

• dogs are reservoirs

how do hookworms work?

they stick to the intestinal wall and suck blood → makes patients anemic

what are mollusca?

mollusks are soft bodied animals that are mostly protected by a hard shell

which organisms are mollusks?

snails, slugs, oysters, clams, octopuses, squids

what is the lifecycle for mollusca?

includes a ciliated larva called a trochophore

what are mollusks composed of?

a body cavity and complex organs

what are the three most diverse clades/types of mollusks?

• gastropods: snails and slugs

• bivalves: clams, scallops, oysters

• cephalopods: squids and octopuses

what is the body plan of a mollusc?

• foot → locomotion

• visceral mass → contains most of the internal organs

• mantle → folds of tissue over visceral mass, secretes a shell in some molluscs

• mantle cavity → water-filled cavity that houses gills

• radula → rasping organ that’s used to scrape food

what are gastropods? from mollusca

can be freshwater/saltwater or terrestrial

• terrestrial have no gills, and the mantle lining helps with gas exchange

what is the composition of gastropods?

• most have a single spiral shell

• distinct head with eyes @ tentacle tips

• SLUGS lost their shells and mantle

what do gastropods do when they’re threatened?

retreat into their shells

what organisms are bivalves?

clams, oysters, mussels, scallops

what is the composition of bivalves?

• shell divided in half, but HINGED

• mantle cavity has gills for feeding and gas exchange

• muscular foot is present for digging and anchoring

  • sessile → secretes thread to attach to rocks, boats, docks

• eyes are @ edge of mantle

are bivalves suspension feeders?

most are!

• have mucous-coated gills to trap food which cilia will sweep into mouth

bivalves are sedentary where?

sand or mud

what are cephalopods?

fast, agile predators

what is the composition of cephalopods?

• CAN have an external shell (nautilus), a small internal shell (squid), or no shell at all (octopus)

• have beak-like jaws and a radula to crush/rip prey

• mouth @ foot

• foot is present, but drawn out into long tentacles to catch/hold prey

• large brains

• good sense organs like eyes → focuses light and retina provides clear images

what can you say about octopuses and cephalopods?

• MOST INTELLIGENT invertebrates

• lives on sea floor eating crabs, etc

• moves rapid via forcing a jet of water out of mantle cavity

• coloured for communication and camouflage

what can you say about colossal squids and cephalopods?

• lives in deep ocean near antarctica

• largest invertebrate → 13m

• eyes are 35cm in diameter

what are annelids/annelida?

segmented worms → they’re called “segmented” because their bodies are repeating ring like segments

• ex: earthworm