Characteristics Unsegmented worms Simplest animals with Bilateral symmetry No specialized circulatory or respiratory system uses diffusion to transport oxygen and nutrients ID: 779035
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Slide1
Phylum Platyhelminthes
Flatworms
Slide2Slide3Characteristics
Unsegmented worms
Simplest animals with
Bilateral symmetry
Slide4No
specialized
circulatory or respiratory system
(uses diffusion to transport oxygen and nutrients)
Excretes
by
diffusion
Slide5Cephalization
(
sense organs and
nerve cells gathered into a head region)
Primitive organ systems with true
organs (digestion, excretion)
Slide6Sexual and asexual reproduction (hermaphroditic but don’t self fertilize)
Free-living and
parasitic
mobile
Slide7Free-Living Flatworms(Aquatic) eg. Planaria
Slide8Planaria
– cross-eyed fresh water worm
Slide9Free-living Flatworms
PLANARIA
Both marine and
freshwater
Most are small
(less than cm and few mm thick)
Slide10Primitive nervous system allows for coordination of body movements
Simple eyes that detect
light
changes (respond to stimuli!!)
Slide11Locomotion:
cilia
help glide through water, muscles allow them to twist and turnFeeding :
Some are carnivores , others are scavangers.
Gastrovascular cavity with one opening at the end of the muscular tube called a pharynx.(used to suck food in to gastrovascular
cavity)
Gastrovascular
cavity-intestine with many braches.
Intestine secrete enzyme to help break down food.
Digested food can diffuse from the intestine into nearby cells.
Slide12Reproduction
Sexual – one worm delivers sperm, while other receives, egg laid in clustersAsexual by fission
Slide13Parasitic Flatworms (Flukes)
eg. Tapeworms
Slide14Slide15Parasitic FlatwormsTAPEWORMS!!
Scolex
Proglottids (sections) form at anterior end
Slide16Found inside and
outside hosts
If inside cannot afford to grow too large or it will kill
its host.Tapeworm: Have a scolex
(head) with several suckers and ring hooks ---attach to intestinal wall.Some can reach up to 30 m in length (found in a sperm whale) Human tapeworms can be 7 m
Slide17Live in intestines - Feed on
blood, tissue, fluids and pieces of cells
Lack : sensory organs, coordination for mobility, digestive system
Slide18Highly developed reproductive system capable of producing hundreds and thousands of egg and sperm.
No digestive tract – absorb food as it passed by
Slide19developed
a way to maximize absorption of nutrients from their host
being flat
VERY long
(which increases their surface area to maximize the absorption of
nutrients)
Slide20Schistosoma
mansoni
Life cycle:
Swimming larvae
Burrow into snail
Reproduce asexually
Break out of snail
Swim in water
Bores through skin of human to blood vessels and then intestines
Blood vessels leak eggs into intestines
Very sick human
Slide21Tapeworm life cycle
Mature
proglottids break off posterior
Eggs are releasedAnimal eats contamination
Forms a dormant cystHuman eats
Hatch in host
Slide22