TCU - BIOL 102 - Biology II Exam #2 Study Guide - Study Guide

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Biology II Exam #2 Study Guide -Biochemical and molecular information tells us that animals evolved about
700 million years ago -Animals are a relatively new species and they have a lot of morphological
diversity and a great distribution of diversity -Due to their form, animals are incredibly diverse whih give us an advantage
to survive in ertain environments What makes an animal? -All animals are heterotrophic (by ingestion)
-They reproduce sexually
-They are eukaryotes
-Multicellular
-No cell wall (the biggest different that is only true to animals and no other
organism on earth -Allows for certain conditions to occur that does not happen in other organisms
-Produce collagen (protect our cells)
-Share certain developmental similarities, most notably a gastrula stage
-Most have a larval stage
-Most animals and only animals have Hox genes that regulate the
development of bosy form
-Animals can displace their entire body from one place to another or move
bosy parts *There are exceptions to nearly every criterion for distinguishing animals
from other life-forms Cell Structure: With an absence of cell wall, our cells have
motility

Reproduction and development -Most animals reproduce sexually, with the diploid stage usually dominating
the life cyucle
-After a sperm fertilizes an egg, the zygote undergoes rapid cell division
called cleavage
-Cleavage leads to formation of a multicellular, hollow blastula
-The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues Animal Body Plans -Some have no symmetry, or they have radial or bilateral symmetry

-Sponges are the only animals without true tissues
-All other animals have two or three germ layers [ diplobastic (two) and triploblastic (three) ]
-Ectoderm, Endoderm, and Mesoderm -Body cavities are derived from the mesoderm, so its found in most triploblastic animals -There are three classifications of body cavities -Any organisms without symmetry will not have true tissues
-Radially symmetric organisms are diploblastic and bilaterally symmetrical are triploblastic Sponges: the most simple animals

-Phylum Porifera
-Two layers of cells separated by a jelly like matrix, coated over a structural skeleton -No symmetry, nerves, guts, reproductive organs etc
-Intracellular digestion (phagocytosis)
-Totipotent - stem cells to differentiate into any cell in an organism including embryonic tissue is an important distinguishing quality -Suspension feeders
-Have spicules made of calcium carbonate (hard) , silicon dioxide (glass) , or
spongin • Multicellular, but just barely: no true tissues, practically colonial except cells can’t live on their own – Cells can re-differentiate – Can even filter a sponge through cheesecloth and have it re- assemble on the other side?
-It will because of the amoebocytes. It will form another cell • Two key points in sponge biology – Sponges use voltage-gated Ca + channels in communication to coordinate this activity – Sponge larvae have sensory cells that allow them to detect and react to environmental stimuli such as light • Other branches of life have some of these features, so what’s the big innovation? – Voltage gated Ca + channels  voltage gated Na + channels somewhere along the animal line (but not in sponges) – Voltage gated Na + channels made possible electrically excitable cells: muscle

*They are gated meaning that they are not always open -However, the function of the sodium potassium pump is not enough by itself
to bring us to resting potential -The pumps require extra energy and an extra ion, so we are adding additional complications -But we keep it in the family, so sometimes potassium will leak out of the cell
-The leaky potassium ions help to bring us to resting potential
-We need three transport proteins, and we can take the sensory information
fro the outside to our muscles

Neural action potentials -Signals cause the sodium channels to open
-If enough sodium rushes into the cell, it causes depolarization which is the
cell becoming more positive therefore the axon hillock is also depolarized
-Depolarization results in a wave of opening voltage-gated sodium channels -This means that an action potential is occurring -Depolarization at the axon terminal triggers a release of
neurotrnasmitters
-This process is very fast -Unmyelinated cells send signals at speeds of about 2 m/s while myelinated cells increase the rate by about 50X due to the salutatory
propagation *Know the steps of an actin potential in detail*
First the cell must reach threshold or else an action potential will not occur
because the strength doesn’t change, the frequency does. Once the cell has
reached threshold, the sodium channels open causing sodium to flood into
the cell causing it to become more positive, depolarize, and once the cell
has reached its maximum peak, the sodium channels close and the
potassium channels open. When the potassium channels open, it cause the
cell to repolarize (become more negative) and during all of this a new
action potential cannot occur. Once the cell has reached the refractory

period is when another action potential may be fired. During the refractory
period, the cell has become hyperpolarized (more negative than it should be)
and that’s when the potassium channels close and the cell goes back into its
resting state Neurons are classified by the direction in which they send
information Sensory: they travel from the sensory receptors to the central nervous
system
Interneuron: they travel between the sensory and motor neurons
Motor: they travel away from the central nervous system to muscles and
glands **Anything can be an environmental cue** -Heat, touch, electricity, hear, smell, light, etc