Life 103 Exam 3

Body Symmetry, Body Cavities, & Protostome vs. Deuterostome embryonic development (focus on the differences, not every single detail)

Nervous and muscle tissue are defining characteristics of animals

Choanoflagellates are the closest living relative to animals

Cleavage is the rapid cell division that an embryo undergoes after fertilization

Cleavage leads to the formation of a blastula

The blastula undergoes gastrulation, which creates three tissue layers: endoderm, ectoderm, mesoderm

Radial symmetry means similar parts are arranged regularly around a central axis

Bilateral symmetry means one half of an organism is a mirror image of the other half. Bilateral organisms have a central nervous system.

Diploblastic means an animal has endoderm and ectoderm

Triblastic means an animal as endoderm, mesoderm, and ectoderm

Coelom is a true body cavity made from mesoderm

Pseudocoelom is a body cavity derived from the mesoderm and endoderm

Protostome development is determinant and spiral. Mouth is made from the gastrula

Deuterostome development is radial and indeterminate. Anus is made from the gastrula

Examples of organisms/groupings of organisms that fall into the categories described above in #1:

a. Sponges lack true tissues

Cnidarians are diploblastic with radial symmetry. They use tentacles with cells called cnidocytes that contain nematocysts that contain a stinging thread.

Flatworms (platyhelminth) (spiralia) are triploblastic with bilateral symmetry. Gas exchange takes place across their skin. Dorsoventrally flattened acoelomates

Segmented Worms Annelids, Coelomates with segmented body wall and internal

organs

Nematodes Ecdysozoans, pseudocoelomates

Arthropods Ecdysozoans, body plan consists of a segmented body, hard exoskeleton, and jointed appendages. 

Hexapoda= insects→wings are extensions of the cuticle. Incomplete metamorphosis is when young are smaller versions of adults. Complete metamorphosis is when young occupy different niches than adults. 

Echinoderms (sea stars), deuterostomes and coelomates

b. Vertebrates are chordates with a backbone

Chordates have a notochord, post-anal tail and a hollow dorsal nerve cord at some point in their lives. Pharyngeal slits develop into parts of the ear, head and neck. 

Gnathostomes are vertebrates with jaws and four sets of HOX genes. Jaws increase the amount of food sources available. 

Fishes can be ray finned and lobe finned (muscular pelvic and pectoral fins.) 

Tetrapods are gnathostomes with limbs. They have a fused pelvic girdle and necks. Tiktaalik has fish and tetrapod characteristics. 

Amphibians have aquatic larvae and terrestrial adults

Amniotes are tetrapods with a terrestrial adapted egg

Reptiles most reptiles are ectothermic (absorb outside heat).

Birds are endothermic, and produce heat through metabolism. Therefore they must eat more than ectotherms. 

Mammals are amniotes that have hair and produce milk in mammary glands. The bones make up the middle ear, and one dentary bone makes up the bottom jaw. More involved in raising offspring. Humans are a type of mammal called a Eutherian, as we spend most of our development in the uterus. 

Primates have a large brain and short jaws. Forward looking eyes that allow for depth perception. 

Humans are bipedal primates that share a common ancestor with apes. 

Heat transfer examples & regulatory mechanisms (homeostasis, positive vs. negative feedback)

Form and function are correlated. 

Convergent evolution leads to similar traits is different organisms in similar environments

High surface area to volume ratio increases efficiency

Homeostasis is the maintenance of internal balance despite external factors

Negative feedback is when a variable is returned to normal range

Positive feedback amplifies a response