lecture 14 Flashcards
1
Q
using body plans to build phylogenetic trees
A
- far left is the ancesteral colonial protist
- eumetazoans: animals with true tissues
- sponges: have mo true tissues
- animals with radial symmetry vs animals with bilateral symmetry
- most animals have bilateral symmetry-bilaterians
- further divided into two clades on the basis of embryology
- deuterostomes and protosomes
2
Q
sponges
A
- stationary animals
- sedentary
- most marine, some fresh water
- some are radially symmetrical
- most lack body symmetry
- resemble thick walled sec with holes
- water is drawn through the pores into a central cavity which then flows out through a larger opening
- more complex sponges have branching water canals
3
Q
sponge body consists of two cell layers
A
- which are seperated by a gelatinous region
- inner layer of flagellated cells choanocytes help sweep water through the sponges body
- amoebocytes wander through the middle body region
- produce supportive skeletal fibers composed of flexible protein called spongin and mineralized particles called spicules
- sharp spicules may also protect the large opening
4
Q
how do sponges feed?
A
- sponges are suspension feeders
- animals that collect food particles from the water
- the food is passed through some sort of food-trapping equipment
- feed by collecting food particles from water that stream through their pores
- chanocytes trap food particles in mucus on membranes that surround the base of their flagella and then engulf the food by phagocytosis
- the amoebocytes pick up food packaged in food vacuoles from choanocytes and digest it carrying the nurtients to the other cells
5
Q
adult sponges
A
- adult sponges are sessile (anchored in place)
- they are unable to escape predators
- consequently sponges produce defensive compounds such as antibiotics and toxins to deter pathogens, parasites and predators
- the simplest of all of the animals
- no nerve or muscles
- individual cells can sense and react to environmental changes
- no true tissues
- thought to have evolved from flagellated protist ancestor
6
Q
cnidarians
A
- eumatozoan: have true tissues
- these are one of the oldest groups within the emumatozoa
- includes: hydras, jellyfish, and corals
- radial symmetry
- only two tissue layers
- outer epidermis and inner cell layer that lines the digestive cavity
- jelly-filled-middle region which may contain scattered amoebid cells
- have contractile tissues and nerves in their simplest form
- incomplete gut or gastrointestinal cavity
- mouth and no anus: single opening
- tentacles surround the mouth opening to assist the trapping and intake of food
7
Q
there are two main body forms within the group cnidarians
A
-some species occur in only one form where as others exist in both forms during the life cycle
1. medusa
-motile’-swimming
-mouth facing downwards
-organism is umbrella shaped with a thick middle layer
composed of a viscous jelly-like material
ex) jellyfish
2. polyp
-stationary
-tubular
-tentacles face up
-colonial aggregations are the most common
ex) sea anemone
8
Q
cnidocytes
A
- unique stinging cells
- function in defense and prey capture
- the prey is paralyzed by toxin released during the sting
- cnidocytes are found throughout the epidermis and tentacles
- nearly all cnidaria are carnivorous
- feeding predominately on small crustateans and other plankton that is captured by the tentacles
- prey enters the gastrointestinal cavity via the mouth where digestion takes place using extracellular enzymes
9
Q
platyhelminthes
A
- flat worms
- bilateral symmetry
- thin and ribbon like
- simplest of the bilateral
- marine, freshwater, and damp habitats
- one opening to the gastrointestinal cavity
- GI cavity contains fine branches distributing food throughout the animal
10
Q
platyhelminthes: planarians
A
- free living flat worms
- head with a pair of light sensitive eyespots
- flap at each side of the head to detect chemicals
- dense packs of nerve cells function as a brain
- a pair of nerve cords connect with small nerves that branch throughout the body
- live on undersurfaces of rocks in steams and freshwater ponds
- highly branched GI cavity
- sucks food in from the mouth at the tip of a muscular tube
- use cilia on their ventral surface to crawl in search of food
- also have muscles that enable them to twist and turn
11
Q
platyhelminthes: flukes
A
- parasitic
- have tough protective covering
- suckers that attach to their host
- reproductive organs occupy almost the entire interior of these worms
- complex life cycles
- intermediate hosts in which larva develop
- larva infect final host where they will live as adults
- ex) blood flukes that cause schisosmiasis in humans spend a part of their life cycle in snails
12
Q
platyhelminthes: tapeworms
A
- inhibit the digestive tract of vertebrates as adults
- ribbon like body
- this is the most evolutionary advanced of all of the flatworms
- lacks a gut
- nutrients are taken up from the host across the wall of the worm body
- the nervous system is also reduced
13
Q
nematodes
A
- roundworms
- these are cylindrical worms with a blunt head and a tapered tail
- they are covered by a tough, non-living cuticle
- periodically shed
- used as protection and to resist dehydration
- pseudocoelomates
- complete digestive tract
- a mouth and an anus
- free-living
- soil dwelling
- body is composed of a fixed cell number
- some are parasitic
- big agricultural pests, attack animal and plant roots
- some cause animal diseases such as heartworm
14
Q
molluscs
A
- most diverse group of invertebrates
- terrestrial, marine, and fresh water organisms
- have seperate sexes
- bilateral symmetry
- 3 tissue layers
- body is composed of a small, not well defined head, large dorsal visceral mass and a broad, flat ventral foot
- visceral mass covered by the mantle which secretes the shell
- shell is unique character of the molluscs
- shell is composed of calcium carbonate
- contains gills for respiration
- have a true coelom
- have a circulatory system
- feed with a structure called radula
- life cycle includes a ciliated larval stage called a trochophore
15
Q
molluscs three major classes
A
- gastropods
- bivalves
- cephalopods
