Lecture 25 Flashcards
Evolution of Animals: When did animals begin to evolve? From what did they evolve?
700 years ago from single-celled Eukaryotes.
What is a Eukaryote:
A cell with a nuclear wall with membrane-bound organelles.
When did the Cambrian Explosion Happen:
535 to 525 million years ago. Gave rise to the common large forms of present-day animals.
What was the first animal group during the Cambrian Explosion?
Sponges.
What is the scientific group (phylum) for the sponges?
Porifera.
How do Sponges eat and how?
Sponges are filter feeders, they capture food through particles suspended in water.
How does the water move through the sponge for filter feeding?
Water moves through the body’s pores, through the central cavity, and out through the opening at the top.
Sponges do not have “true tissues” what does this mean?
Instead of “true tissues” its has groups of cells that function as one unit, rather than having specialized cells that function as a singular unit. A true tissue has an ectoderm or and endoderm. A sponge doesn’t have a true gastrula which during embryogenosis when the embryo of the egg is formed during fetilization.
Sponges: Parts of the sponge?
Choanocyte: Cells that surround the central cavity. Create a current that draws water through the pores and forces water out of its cavity during filter feeding.
Pores: Water enters through its pores in the body wall of the sponge. The cells in the wall are separated by a gelatinous matrix, similar to the skin of mammals.
Amoebyctes: Cells that transport nutrients to other cells in the sponge body.
What are tissues:
Collections of specialized cells that act as a functional unit, isolated from other tissues. Formed during embryogenesis from the germ layers to develop organs and tissues.
Types of Tissues:
Ectodderm, Mesoderm, Endoderm
What is ectoderm:
The outer germ layer gives rise to the outer covering and the central nervous system.
What is the mesoderm:
Fills the space between the ectoderm and the endoderm and gives rise to muscles and most other organs.
What is the endoderm:
The innermost germ layer gives rise to the digestive tract and the lining of internal organs.
What are Cnidarians:
Cnidarians arose about 680 million years ago and have diversified into both sessile and motile forms, including hydrozoans, jellies, and sea anemones.
What do Cnidarians have in common with all other animals?
True tissues. Every animal apart from sponges and a few other groups have tissues.
Three common types of Cnidarians:
Hydrozoa, Scyphozoa, and Anthozoa.
What are Jellyfish?
Scyphozoa, are bioluminescent, and some stun their prey with nematocysts, specialized cells, located on their tentacles.
Types of Symmetry:
Bilateral Symmetry, Radial Symmetry, and Asymmetrical.
Radial Animals Typically:
Drift or weakly swimming (planktonic), or are attached to substrate (sessile).
Bilateral Animals Typically:
Move actively the CNS to enable coordinated movement.
Phylum: Platyhelminthes
The simplest animals are bilaterally symmetrical, and triploblastic (3 cell layers) and lack a body cavity.
Most bilaterians possess a body cavity (coelom). Which is used for?
Suspending organs with fluid to cushion them, and enable internal organs to move independently of the body wall.
Allows internal organs to move independently of the body wall.
Types of Coelom:
Coelomate, Psuedocolelomate (fake, meaning not having a body cavity not dervied from the mesoderve instead being drived from the blastocoel) , and Acoelomate (no fluid between wall and mesoderve).
Phylum: Nematodes and Rotifera: What makes these groups different?
Embryonic Development within the animal.
What is the protosome?
“First-mouth”
What is the deuterostome?
“Second-mouth”
Phylum: Mollusca: What are its traits?
The second largest animal phylum, has a true coelom, and a free-swimming larval stage.
What is segmentation:
The division of the body into a series of smaller segments.
What are the advantages of segmentation:
Other sections might be able to perform the function of a damaged section.
Segments can be more independent - flexible and capable of complex movement.
Phylum: Annelida: What are Annelids?
Annelids are segmented worms that live primarily in marine or freshwater habitats.
Annelida Traits:
Exhibit organ system level organization.
Their body is segmented.
They respire through their body surface.
They have a well-developed circulatory and digestive system.
Regeneration is a very common characteristic of the Annelids.
Phylum: Arthropoda: How many species
1,000,000 species known currently.
Arthropoda: What are they?
Arthropods have segmented exoskeleton and jointed appendages.
What groups are part of phylum arthropoda?
Insects, millipedes, crabs, and arachnids.
Arthropod Origins: Where are they found and why.
Members of Arthropoda are found nearly in all habitats of the biosphere and their body plan attributes to their success.
