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What is a meeting evolutionary innovation that occurred among cnidarians?
Extracellular digestion of food
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What happens when food is trapped by a sponge chaonocyte?
it is directly taken to endocytosis and digested intracellularly.
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Where in cnidarian's is food digested?
Extracellularly in a digestive cavity
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What has been retained by all of the more advanced groups of animals?
Extracellular digestion of food.
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What are a cnidarian's two basic body forms?
Medusae & Polyps
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Describe the characteristics of a medusae?
Free-floating, gelatinous, contains lots of mesoglea, the mouth and tentacles face downward, and umbrella shaped
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Describe the characteristics of polyps.
they are cylindrical, pipe shaped, have a little mesoglea, the mouth and tentacles face upwards
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What does bilaterally symmetric mean?
Animals have left and right halves that mirror each other.
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Name the 4 parts of a bilaterally symmetric animal?
Describe them Dorsal- top surface of animal, Ventral- bottom surface, Anterior- front end, Posterior-back end
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Bilateral symmetry a major evolutionary advancement among animals?
It enables different parts of the body to become specialized different ways
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What is cephalization?
The evolution of a head end
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Animals with heads are often ______?______ and ______?______.
Active and mobile
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They move through their environment headfirst with sensory organs concentrated in front so the animals can sense what?
Food, danger, and potential mates
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What are the simplest of all the bilaterally to symmetric animals?
Flatworms
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How many species of the flatworms exist?
20,000
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Flatworms are the ___________ animals that have organs
Simplest
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What is an organ?
A collection of different tissues that work together as a unit to perform a particular function
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Describe a flatworm
Soft body to animals that are flattened from dorsal-ventrally
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What are flatworms sense organs called?
Eyespots
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What can eyespots do?
Detect light but cannot focus
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What is a flat worms digestive tube or gut surrounded by?
Tissues or organs
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What are the organs?
Testes and ovaries
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Why are flatworms called solid bodied worms?
They have no body cavity between their digestive track and skin
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What is the solid-body construction called?
Acoelomate meaning "without" "body captivity"
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Why must flatworms be thin?
Because of their acoelomate body design
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Flatworms have no circulatory system so what and what can pass through the solid body by diffusion?
Oxygen and carbon dioxide
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What is an advantage of a thin body of a flatworm?
Shortens distant that the gases must travel to reach each cell.
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What is the only opening to the gut?
The mouth
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What enters and exits the mouth of a flatworm?
Food enters ; waste exits
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Some flatworms are ____________ but many are ____________.
Free-living ; parasites
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What is the magor advancement in fatworms?
bilateral symmetry
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