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UA / Biological Sciences / BSC 116 / What is the role of glia in the cns?

What is the role of glia in the cns?

What is the role of glia in the cns?

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School: University of Alabama - Tuscaloosa
Department: Biological Sciences
Course: Principles Biology II
Professor: Jennifer howeth
Term: Summer 2015
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Cost: 50
Name: BSC 116- FINAL EXAM STUDY GUIDE
Description: Here is the FINAL EXAM STUDY GUIDE!! This guide is in an outline style, color coded format with supplemental images for further understanding.
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**BSC 116 Final Exam STUDY GUIDE** 


What is the role of glia in the cns?



Lecture 32-43 

Lecture 32: Neurons 

Synopsis: neurons convey information from cell to  cell

∙ chemical and electrical potential moves across the  membrane

o action potential

∙ action potential depends on depolarization of the  neuron

∙ connections between cells (synapses) are usually  chemical and involve neurotransmitters.

**Animals (1)receive information (2)process (3) respond sensory input (received info) goes into the central  nervous system, response is transmitted by the  peripheral nervous system 


It is a center for learning, emotion, memory, and perception, what is it?



Don't forget about the age old question of What are the characteristics of sound exchange errors (garrett 1975)?

DEFINITION:  

neurons= specialized cells that conduct and store  info in the nervous system

Setup If you want to learn more check out What is the preparation of phenols?

∙   Cell body: houses most of cytoplasm, nucleus etc. ∙   Dendrites: branched extensions at receiving end ∙   Axon: extends from neuron to the cell it acts on We also discuss several other topics like What are the functions of the integument?

o Axon hillock: where the axon joins cell body,  signal gen.

Function 

∙ Becomes electrically excited conduction down axon ∙ Synapse=connection b/t neurons

o Excitement (chemical)

o Synaptic terminal in the presynaptic cell  releases neurotransmitters.  


What are the four stages of getting a stimulus to the brain?



o Postsynaptic cell may or may not become  electrically excited by the neurotransmitters ∙ Neuron= on/off switch

∙ Inside negatively/positively chargednot  

excited/excited

 ∙    Charge determined by movement of ions 

DEFINITIONS: Don't forget about the age old question of What is the difference between recall and recognition?

 Sensory neurons=transmit info from sensors  that detect external stimuli or internal  conditions

 Interneurons= from the local circuits  connecting neurons in the brain

 Motor Neurons= transmit signals to muscle  cells  

 Glial Cells= nourish, insulate and regulate  neurons

-Neuron at Rest

DEFINITIONS:  

 membrane potential=voltage difference across  cell membrane as a result of unequal  

distribution

 resting potential=membrane potential of a  neuron that is not excited

∙ Resting cell maintains K+-Na- gradient

o ATP powered sodium potassium pump

o Ion channels let ions move down their gradients o Net movement of charge is what creates voltage potential

***when a neuron is excited, the membrane  potential goes from negative to positive

DEFINITION:  

 gated ion channels =respond to some stimulus  by opening/ closing  

 voltage gated ion channels= respond to  change in membrane potential

 Hyperpolarization= membrane potential more  negative  If you want to learn more check out What is the difference between the method of agreement and the method of difference?

∙ Depolarization (less negative) of membrane potential activates voltage gated Na+ channels

o Positive feedback: leads to further depolarization and more Na+ channels opening

o Action potential: massive, rapid depolarization

**Action potentials are propagated along axons ∙ During falling phase and undershoot, Na+ channels  activated  

o Refractory period: time between action  If you want to learn more check out What is the goal of the sport management professions?

potentials

∙ Signal propagates because action potential in one  area of axon depolarizes neighboring region ∙ Activation of K+ and inactivation of Na+ channels  during refractory period  

∙ Speed of propagation increases with axon diameter  and “insulation” by glial cells

**Vertebrates and neurons are insulated by glial cells ∙ 2 kinds of glial cells provide a myelin sheath around  axons: electrical insulation

o wrap axons in multiple layers of cell membrane  o no leakage to dampen effect with distance o oligodendrocytes in CNS 

o Schwann cells in PNS 

∙ Insulation allows depolarization to propagate  farther/faster

∙ Voltage gated Na+ channels limited to gaps in myelin sheath: nodes of Ranvier

o Depolarization jumps from node to node

**Info passes in chemical form from 1 neuron to  another  

In vertebrates, chemical synapses more common, NOT  electrical synapses

DEFINITIONS:

∙ Neurotransmitter=pre-synaptic chemical  released by neuron

 Presynaptic axon terminal= neurotransmitter  packaged into synaptic vesicles

∙ Postsynaptic membrane has ligand-gated ion  channels that bind neurotransmitter.

o Binding change in potential

o Excitatory postsynaptic potentials: depolarize  membrane slightly

o Inhibitory postsynaptic potentials: hyperpolarize  membrane slightly

**The Number and type of synapses determines  the response

postsynaptic potentials graded rather than all or  nothing

∙ Don’t exceed threshold then fade

∙ Multiple potentials can build up

o Temporal summation- series of potentials from  same synapse 

o Spatial summation- potentials from different  synapse on cell  

∙ Inhibitory potentials can cancel out excitatory  potentials

Lecture 33: Nervous Systems 

Synopsis:  

-neurons convey information from cell to cell -neurons are arranged into networks

-nervous systems are large networks of neurons

**different taxa= different nervous systems** ∙ Cnidarians: diffuse nerve net

∙ More complex animals: nerves of multiple neurons o Central nervous system (CNS) brain+ nerve  cord(s) running body length 

 Protostomes have ventral nerve cord

 Deuterostomes have a dorsal nerve cord

o Peripheral nervous system: ganglia and nerves  outside CNS 

!!Vertebrate CNS= large brain and spinal cord!!

DEFINITION

 Brain: is where all stimulus and voluntary  behavior is processed

 Spinal cord: carries impulses to and from brain -mediates reflexes: involuntary movement  

both made of grey matter ( NON-MYELIN) and  white matter (MYELIN)

**both derives from hollow dorsal nerve cord

∙ Central canal of spinal

∙ Ventricles of the brain

∙ Both filled with cerebrospinal fluid

Role of glia in the CNS: nourish, support and regulate  the functioning of neurons in the brain and spinal cord

DEFINITIONS:

 Radial glia= embryonic glia that form tracks  along which newly formed neurons migrate  from the neural tube, the structure that gives  rise to the CNS

 Astrocytes= facilitate info transfer at synapses and sometimes release neurotransmitters;  initiates formation of the blood- brain barrier  during embryonic development

 Radial glia + astrocytes= can act as stem cells, generating new neurons in glia

 Oligodendrocytes= myelinate axons in the CNS  Schwann cells= myelinate axons in the PNS  Microglia= immune cells that protect against  pathogens

 Ependymal cells= line ventricles and promote  circulation of cerebrospinal fluid

**The PNS carries info to and from CNS*** DEFINITIONS:

 Cranial nerves= connect brain with head  Spinal nerves= connect spinal cord to rest of  body

 Afferent neurons= bring info to the CNS  (sensory)

 Efferent neurons= carry info from CNS

-motor system: skeletal muscles; voluntary (&  reflexes) 

 respond to external stimuli

-autonomic nervous system: smooth and  cardiac muscle, glands etc. ; involuntary 

 sympathetic division: arousal, “fight  or flight”

parasympathetic division: calming  

“rest and digest”

enteric division: digestion

**Brain begins as 3 bulges of neural tube, develops into

∙ Hindbrain & midbrain 

 o Brainstem= midbrain+ pons+ medulla  Homeostasis, coordination, info sharing

 Attention, alertness, motivation

 o Cerebellum: coordinates movement, hand eye coordination 

∙ Forebrain 

 o Diencephalon= thalamus+ hypothalamus+  epithalamus 

 Homeostasis, coord. Sensory info, circadian  rythms

 o Cerebrum: center for learning, emotion,  memory, perception 

 80% of brain

 outer cortex of grey matter  

 connected by corpus callosum

**Sleep and emotions are locally regulated in the  brain

∙ controlled in part by reticular formation:diffuse  network of neurons in the core of the brain stem;  filters incoming info to determine what gets to  cerebellum 

∙ more info to cerebellum= more alert/awake  ∙ Pons and medulla: regulate sleep 

∙ Biological clock: regulates sleep cycles coord. By  group of neurons in hypothalamus and melatonin  from the pineal gland 

∙ Limbic system: borders the brainstem, responsible   for emotions  includes amygdala, hippocampus  and thalamus 

**Cerebral Cortex controls things we make  decisions about 

4 LOBES 

1. Frontal

2. Parietal

3. Occipital

4. Temporal

 ∙    Sensory info received from thalamus 

o Received in primary sensory areasassociation  areas to make sensefrontal association area to  be acted on

∙   Different functions localized in different areas o Broca’s area: controls muscles in the face, active during speech generation 

o Wernicke’s area: active when speech is heard,  facilitates comprehension 

∙   Lateralization: 2 hemispheres not identical in  function

3 Process determine structure of the NS during embryonic development 

1.Gene expression, signal transduction, etc.  establish structures

2.Huge neuron die-off

a.Not in right place= die off

b.50% lost

3.Synapse reconfiguration

a.Each neuron initially forms more synapses  than needed  

b.Gets rid of extra

 ∙    Learning and memory based on neural plasticity after embryonic development 

o synaptic connections weaken or strengthen o memories form by rearranging connections in  hippocampus

 short term= store stimuli for short period to  see if important

 long term= rearrangements in cerebral  

cortex

∙   Long term potentiation-ex. Of how synaptic  connections changed

o Frequent excitation of a synapse can make the  postsynaptic neuron more sensitive to the  

presynaptic neuron

Neural Diseases 

 •schizophrenia 

 •depression 

 •drug addiction 

 •Alzheimer’s disease 

 •Parkinson’s disease 

Lecture 34: Sensory and Motor Mechanisms 

Synopsis: Different types of receptors code  external stimuli as action potentials

EX: chemoreceptors, mechanoreceptors,  photoreceptors

4 Stages of getting a stimulus to the brain:

1.Reception: sensory cell detects stimulus

2. Transduction: conversion of stimulus to receptor  potential

3. Transmission: if receptor potential initiates action  potential

a. Receptor cell- axon or neurotransmitter

b. Strength of stimulus modulates frequency of  action potential

c. Integration= processing might begin even before transmission

4. Perception: CNS processing of input from sensory  neurons

**Transduction can be modified in 2 ways:

1.Amplification: strengthening the stimulus; adding  energy 

2.Adaptation: become unresponsive to constant  stimulation

Different Types of Sensory Receptors 

 ∙   Chemoreceptors: bind molecules, initiates change  in membrane potential  

 ∙   Mechanoreceptors: deformed or moved to sense  pressure, stretch, motion etc.

 ∙   Electromagnetic receptors: detect light,  electricity, magnetism etc.

 ∙   Thermoreceptors: detect heat and cold  ∙   Nocireceptors: detect pain, like extreme pressure,  chemicals etc.

**Taste and smell both rely on chemoreceptors** ∙   Gustation= taste; detection of tastants in solution

o In animals: taste buds

o In insects: bottom of feet and mouth parts ∙   Olfaction= smell; detection of odorants in air  o Mammals: receptors in upper nasal cavity

**Hearing and balance both based on  

mechanoreceptors**

Hearing= pressure waves in the air deform receptor cells, leads to membrane potential perception of vibrations

∙ Starts with conversion of waves in air to fluid o Outer ear: tympanic membrane (eardrum) vibes o Middle ear: 3 tiny bones transmit

o Inner ear: cochlea receives vibrations

∙ Waves flow down vestibular canal, cause vibrations that stimulate hair cells

o Hair cells releasing neurotransmitter all the time o In one direction- depolarize, in other direction hyperpolarize

∙ Second stimulus has both volume and pitch o Volume- magnitude

o Pitch- frequency

∙ Fish- no need to convert air pressure

o No outer ear- vibes pass from water through  body

 Lateral line system= mechanoreceptors for detecting low- frequency vibrations perceive the direction and velocity of  

water, predators, prey

∙ Insects- have “hairs” that vibrate  

o Some have tympanic membrane  

**Balance requires sensing orientation relative to  gravity and angular momentum**

∙ Many animals have statocysts to sense gravity o Chamber surrounded by ciliated cells  

o Statoliths move around as body moves

 ∙    In mammals. Balance assoc. with ears 

o Inner ear has utricle (horizontal) and saccule  (vertical)  

o Chambers lined with hair cells and little stones  (otoliths)

o Tilt head stones move

o Semicircular canals detect angular momentum **Light Detection**

∙ Photoreceptors: cells that detect light

∙ Light detecting organs

 o Ocelli: simple cup of photoreceptors 

 Creates shadow to determine light direction ∙ Single- lens eyes: functions like camera

o 1 opening with a lens to focus light on a field of  photoreceptors

∙ Compound Eyes: composed of many detectors,  ommatidia

o Insects

o Each facet has own lens

Lecture 35: Sensory and Motor Mechanisms II Synopsis:  

∙ Effector neurons work on muscles

∙ Sliding filament model of muscle function ∙ Contraction is the sum of many twitches ∙ Muscle contraction action

**Complicated integration of signals leads to a  specific response

response can act on the endocrine system,  muscles 

**Skeletal muscle contracts to move skeletal  elements  

∙   Characteristic organization: linear fibers within fibers o Muscle= bundle of fibers running parallel to  bone 

o Fiber= single cell (multiple nuclei) with bundle of myofibrils 

∙ Sarcomere: basic contractile unit of myofibril o Ends of actin fibers line up at ends: z lines o Middle of myosin fibers: m line

o “striated muscles”: array of adjacent sarcomeres ∙ muscles contract by actin and myosin sliding  past each other: sliding-filament model 

 ∙    myosin molecule: long tail and round head o tails of myosin stick together in thick fiber  o head is where all the action is  

1.Head binds ATP (low-energy configuration) 2.Head hyrolyzes ATP to ADP, uses energy to  change shape: head moves forward

3.Head binds to adjacent thin (actin) filament 4.Head releases ADP but holds on to actin a.Changes shape to pull thick filament  against thin

5.Binding new ATP causes head to release cycle restarts

***Ca 2+ & regulatory proteins control  contraction of muscle fibers***

∙   2 sets of regulatory proteins are bound to the  thin (actin) filaments

o tropomyosin: coils around actin 

o troponin complex: arranged along  

tropomyosin 

o proteins block myosin binding-sites: inhibits  actin-myosin interaction

∙   Ca2+ in cytoplasm binds troponin complex:  results in exposure of myosin binding sites

 !!An Action potential  myofibril contraction!!

1. With action potential, motor neuron releases  acetylcholine (neurotransmitter), binds to receptors  on muscle

2. Triggers action potential, transverse tubules (ext. os  plasma membrane) carry AP deep into muscle cell 3.AP causes sarcoplasmic reticulum to release Ca 2+ 4. Troponin complex and tropomyosin move out of the  way

5. Sarcomere contracts

6. When motor neuron stops firing, Ca 2+ pumped  back to SR

7. Troponin complex and tropomyosin move back in the way, fiber relaxes

8. Like action potential, muscle fiber contraction is “ all or –nothing”, twitch

**Whole muscle contraction is the sum of many  twitches!!! 

∙ Graded

 ∙    Each fiber controlled by 1 motor neuron 

 ∙    Each motor neuron controls many fibers 

o Motor unit= all fibers controlled by one neuron  All contract together

∙ Strength of contraction depends on # of neurons  recruited and the size of the motor units that they  control 

∙ Rapid AP’s rapid twitches

o Tension may not be lost bt them= tetanus ∙ “twitches” smoothed out by tendons 

**Some sort of skeleton is necessary to turn  contraction action***

- muscle works in antagonistic pairs 

- many animals like mineralized or chitin skeletons :  rely on hydrostatic skeletons

Lecture 36: Animal Behavior 

Synopsis:  

∙ sensory activity drives animal behavior ∙ environment and genetics influence behavior ∙ natural selection shapes behavior

o optimal foraging

o mate choice and parental care

o sexual selection

∙ problem of altruism

individual behavior: an action carried out by muscles  under control of the nervous system in response to a  stimulus

**For many behaviors, a particular stimulus leads  to a particular response** 

DEFINITIONS:

 Fixed action patterns: sequence of unlearned  acts linked to a simple stimulus

 Signal: stimulus transmitted from one animal  to another

∙ can be visual, chemical, auditory, tactile ∙ pheremone: a chemical cue often associated  with a threat or reproduction

Communication: the transmission and reception of  signals between animals

**the environment of an organism can influence its  behavior**

 innate behavior: traits that are fixed by genotype

individuals with the same genotype can have different  behavioral phenotypes 

DEFINITIONS

 Learning: modifying behavior based on  experience

 Imprinting: formation at a specific stage in life of a long-lasting behavioral response to an  individual or object , includes a sensitive,  critical period

**behavior is the result of complex interactions of  environment and genotype  

DEFINITIONS

 Cross fostering studies: offspring of one  species raised by another

 Twin studies: look at identical twins placed  with different foster families

**ALL types of animals are capable of learned  behavior**

∙ associative learning- associate one stimulus with  another

 o classical conditioning: arbitrary stimulus leads to a certain response 

 o operant conditioning: trial- and- error learning ∙ spatial learning- maintaining an internal map ∙ cognition- reasoning, awareness

∙ problem-solving- devising solutions to proceed past  obstacles

o social learning: many animals can learn by  observing conspecifics

**The ultimate causes of many behavioral traits  are evolutionary***

3 examples

∙ -optimal foraging 

∙ -mate choice and parental care  

∙ -sexual selection 

∙ foraging= searching for food and eating o optimal maximize bemefit, minimize cost  ∙ mating system= length and number of  relationships between males and females o different species-----different mating  systems/behaviors

 monogamy: long-term pair-bonding 

 polygamy: multiple mated  

∙ polygyny: one male, multiple females 

∙ polyandry: one female, multiple males 

 promiscuous: no pair bonding 

∙ Sexual selection= a type of natural selection;  result of differential mating success when  there is competition for mates

o Leads to sexual dimorphism in phenotypic  traits: appearance and behavior

 Males usually compete to attract females   Males physically compete for females

**Altruism presents a problem for the evolutionary  theory!!

∙ Altruism: doing something that lowers your own  fitness but increases the fitness of others

∙ Inclusive fitness: fitness (REPRESENTATION OF  YOUR GENES IN THE NEXT GENERATION) depends on  your reproduction and that of your close relatives o William Hamilton’s Rule: rB>C

 Weigh the cost/benefit of an altruistic  act

 Cost- the number of offspring that the  act might cost the altruist

 Benefit- # of offspring that an action  will gain the recipient

 R- coefficient of relatedness: avg. # of  genes shared by the 2

 As long as rB>C, benefit outweighs  

cost  

Lecture 37: Into to Ecology 

Synopsis: dist. of species- globally/locally, global  dist. of biomes

**Ecology study of how organisms interact with  each other and their environments

Organism interaction

∙ Individual 

∙ Populations: groups of individuals of same species  ∙ Communities: groups of populations 

∙ Ecosystems: groups of communities 

∙ Landscapes: groups of ecosystems  

∙ Global: the earth: biosphere 

Ecology and Evolutionary Bio

∙ Evolutionary time: populations change to adapt to their environments

∙ Ecological time: response of organisms,  populations, etc. to their environments

Ecology and environmentalism

∙ Not the same thing- science v. advocacy

**No species occurs everywhere

∙ Factors that determine distribution

o Dispersal  

o Behavior  

 Biotic: other living things

 Abiotic: physical factors

Dispersal= movement of individuals to new areas

**organisms may choose to avoid a livable habitat psychological habitat selection 

**species distributions are often limited by other  species

 biotic factors

∙ Species absent b/c other is missing

∙ Species absent b/c other is present  

**species distributions are limited by their  physiological tolerances. 

 abiotic factors 

∙ Temp: too hot/cold

∙ Water: too wet/dry  

∙ Sunlight: esp. for photosynthetic organisms ∙ Geology: the inorganic parts of the habitat o Earth is NOT homogenous for abiotic factors o Summarized as climate

**Shape, tilt, etc. of earth results in broad climatic patterns

∙ Surface curved: areas away from equator get less  intense sunlight

∙ Pattern of heating/ evaporation: variation in  precipitation

∙ Axis rotation tilted 23.5 deg.: seasonal variation in  sunlight

∙ Rotation of the earth: circulation of air/ water  currents

 Local variations in climate  

∙ Proximity to water

o Air changes temp faster than water

∙ Mountains

o Shadow to sunlight

o Altitude and temp

o Rain shadow

∙ Tilt of the earth results in predictable seasonality

Long-term, global variation in climate

∙ Periods differ

∙ Until 15-20k y.a., northern latitudes covered by  glaciers

∙ Species move north as climate warms

Biomes: major habitat types, determined by biotic & abiotic factors

-latitudinal variation in temp., moisture, etc.  leads to latudinal variation in animals/ plants 

Ecotones: areas of transition between biomes **Disturbance community variation, patchiness

!!Aquatic biomes are characterized by salinity and  depth!!

∙ 75% of earth’s surface

o freshwater <0.1%

o marine 3%

o pelagic (open) v. benthic (bottom)

∙ most photosynthesis at surface

o photic v. aphotic

Lecture 38: Population Ecology 

Synopsis:  

∙ variation in life histories

∙ exponential growth

∙ logistic growth  

∙ density dependence v. independence  ∙ metapopulations

**Populations change over time

∙ Population: conspecific individuals occurring in a  particular area

∙ Populations are dynamic

o Gain individuals from birth

o Gain individuals from immigration

o Lose individuals from death  

o Lose individuals from emigration

∙ 3 characteristics to describe populations: o density= number of individuals per unit  area ( or volume)

 boundaries difficult to define

 various methods estimate size/density ∙ mark recapture

o dispersion: pattern of spacing

o clumped: aggregated in  

patches  

o uniform: evenly spaced 

o random: independent of other  

individuals 

o demographics= age and sex structure of the  population

Life table- age specific summaries of survival in  population 

 single cohort construction from birth to death

**Survivorship curve- graphical explanation of life  table

∙  number alive plotted vs. each age  

∙ species have characteristic survivorship  curves depending on life history

reproductive table= fertility schedule

∙ Cost of reptoduction= energy spent on  offspring not spent on parent  

∙ Iteroparity repeated reproduction; multiple  periods 

∙ Semelparity big bang reproduction: all  reproduction concentrated in a single effort  ∙ Trade offs: can’t maximize all reproductive  patterns at the same time

!!As long as there are more births than deaths  POPULATION WILL GROW!!! 

 population growth often regulated by feedback

DEFINITIONS

Carrying capacity: number of individuals that a  habitat can sistain

-limiting factors=energy, shelter, nutrients,  territory

logistic population growth model: incorporates  carrying capacity

∙ K selection- for traits helpful at high densities ∙ R selection- for traits helpful at low densities

***Density dependence is ecological feedback***

∙ When birth/death rates change with population size  they are density dependent

∙ Equilibrium birth=death

∙ Causes of density dependent regulation o Competition

o Disease

o Predation

o Accumulation of wastes  

o Intrinsic factors

∙ Versus density-independent

**Population size is dynamic**

**Populations vary in space as well as time**

∙ Populations connected by dispersal in a  

metapopulation

o Sources: positive population growth , lots of  emigration sinks

o Sinks: negative population growth, lots of  immigration from sources required to maintain  population

∙ Habitat fragmentationmetapopulation

Lecture 39: Community Ecology 

Synopsis:

Interspecific Interactions and regulation of  community structure

Community: composed of 2+ species in space and  time 

Ways that species interact in community: 

1.Competition: -/- species compete for resources  needed for growth, reproduction etc. 

2. Predation: +/- one animal eats another 

a. Prey adapted to hide

i. Cryptic coloration=camouflage

ii. Aposematic coloration=brightly colored

iii. Batesian mimicry= harmless resemblance  iv. Mullerian mimicry= 2 venemous

3. Herbivory: special case of predation, animal eats  plant/alga 

**Competition results from species overlapping  niches** 

Niche: sum of the biotic and abiotic needs of a  species, its place/role in a habitat

 o Wide niche overlaps = competitive exclusion  o Narrow niche overlaps= resource partitioning 

Character displacement: resource partitioning leads to  morphological differences

***Symbiotic relationships

 Symbiosis: close association between species  pairs, where at least one species always benefits

1.Mutualism: +/+ 

2.Commensalism: +/0 

3.Parasitism: +/- 

DEFINITIONS

 Species richness: number of different species  ∙ Relative abundance: proportion of individuals that  belong to each species  

 2 communities can have same richness but  different structures  

!!Trophic Structure!!

∙ -feeding relationships among species  

o -energy moves up from lower levels

o -food chain: producers consumers (herb) consumers (carn)

Energetic Hypothesis: inefficiency of energy  transfer between levels  

DEFINITIONS

 Dominant species: most abundant or greatest  biomass (total of entire population)

 Keystone species: key niches maintaining  community structure ; not necessarily  dominant

 Facilitators: ecosystem engineers

**Communities have top-down and bottom-up  regulation**

3 Possible relationships between plants and  herbivores

o Increase in P, decrease in H  

o Decrease in P, increase in H

o Both

∙ Bottom up: PHC 

∙ Top down: PHC 

**Species richness is maintained by disturbance**

∙ -most communities are not in stable equilibrium ∙ -nonequilibrium model better characterizes most  communities

∙ -intermediate disturbance hypothesis: some  disturbance increases species diversity

!Succession= pattern of species replacement over  time 

DEFINITIONS

 Ecological succession: first colonizers replaced  by other species, which are replaced by other  species  

 Primary succession: beginning without soil  Secondary succession: with soil

*large areas have more species: seen in species area curve

latiudinal gradient: more species closer to the  equator ; higher tropical diversity

Lecture 40: Ecosystems

Synopsis: flow of energy, cycling of nutrients

Ecosystem: sum of biotic and abiotic interactions in an area

**2 abiotic processes central to ecosystem ecology:

1. Flow of energy  

2. cycling of nutrients

!!Both energy and nutrients move through trophic  levels!! 

DEFINITIONS

 Primary producers: autotrophs  

 Primary consumers: herbivores that eat  producers

 Secondary consumers: carnivores that eat  herbivores

 Tertiary consumers: carnivores carnivores that  eat carnivores

 Detrivores/ decomposers: get energy from  detritus (non-living organic material)

**Production is ultimately limited by the amount of energy that enters the system***

∙ primary production: amount of light energy  converted to chemical energy in a given span of time ∙ gross primary production: total 1 degree production  for an ecosystem

∙ net primary production: part stored as organic  matter  

o NPP=Gpp-respiration

∙ Secondary production: new biomass added to  consumers; amount of 1 degree production  converted to consumer

 if plants had all of the needed nutrients, only limited by  light ( because of 1 degree)

limiting nutrient: if adding a nutrient increases  productivity, then it is limiting

eutrophication: increased algal production due to  pollution

**Different nutrients have independent  biogeochemical cycles**

∙ Nutrients cycle through ecosystems

o Biogeochemical cycles: biotic and abiotic

o Inputs/ outputs

o Nutrients sometimes present but unavailable ∙ Nutrients can be available/ unavailable,  

organic/inorganic

∙ 4 most important cycles 

o H2O 

o C 

o N 

o P 

∙ Decomposition= critical for cycling

∙ Detrivores break down org. molecules to inorg. So  they can be used by 1 degree producers  

!Humans enrich the Nitrogen cycle for agriculture! ∙ -farming removes N

∙ -fertilizer adds N

∙ -excess runoff  

Lecture 41: Biodiversity and Conservation Synopsis: major threats to biodiversity

o -habitat loss  

o -invasive species  

o -overexploitation

o -global change

Threats to Biodiversity:  

1.Habitat loss and destruction 

a. Biggest threat  

b. Fragmentation

2.Introduced/ Exotic species 

a. From increase in global travel ( introduced) b.Alter ecosystems

c. Accident/ purpose

3.Overexploitation 

a. Harvested faster than can reproduce

4.Global change 

Human activities habitat degradation/ loss

∙ Agriculture- primary

∙ Natural resource extraction

∙ Urbanization/ infrastructure development ∙ War and violent conflict

∙ Pollution

Consequences of Pollution

∙ Pollutants not broken down by detrivores=biological  magnification: becomes more concentrated in higher  trophic levels

∙ Naturally occurring chemicals released at unnatural  levels  

Invasive Species: An introduced species that  extablishes, expands its range, and has a  substantial impact on native organisms and  ecosystems.

 interact with natives as  

1.Competitors 

2. Predators 

3. Parasites 

Overexploitation 

∙   Hunting

∙   Fishing

∙   Fisheries by catch  

∙   Collecting for trade

**Burning fossil fuels acid rain

∙ Releases S and N

o Combines with water to make sulfuric/ nitric  acids

∙ Kills acid sensitive fish  

∙ Source distant from effects

*Chemicals WE release

∙ CFCs- refrigeration, A/C

o Cl reacts with ozone  

o Ozone breaks down oxygen

o Less ozone =less UV protection

 Hole

o DNA damage  

**Excess CO2 from fossil fuels and increased temp.

∙ CO2, CH4, H2O naturally warm the earth=  greenhouse

∙ Greatest effect at high latitudes

Lecture 42: Conservation Biology 

Synopsis: Human population growth, human  effects, threats

Ecological footprint: measures Human impact Biodiversity: biological diversity 

**anthropogenic (human caused) ecosystem  modification is causing increased extinction rates  

Biophilia: innate tie to nature 

Most common: extinction of species  

∙ -preservation of species genetic diversity  necessary for future adaptation to changing  environment

∙ -community and ecosystem diversity: fates of  species interconnected

Lecture 43: Conservation and Restoration 

Synopsis: approaches to conservation, restoration  ecology, sustainability

***Efforts to protect species revolve around  keeping their numbers from getting too low***

∙ Endangered- when population gets too small o Extinction vortex: small populations lead to  smaller populations which lead to extinction o Minimum viable population (MVP) size: number  of individuals at which a species is able to  

sustain its # and not enter the vortex.

 Depends on species

o Use effective population size rep. estimated  length

!!More efficient to focus on landscapes and  habitats than species!!

∙ Areas= multiple species  

o Large tracts of land to protect against  

fragmentation

 Edges: boundaries between communities or  ecosystems

 Edge effects: increase due to habitat  

fragmentation

 Corridors: strips of habitat that connect  

otherwise isolated habitat fragments,  

facilitates movement and dispersal.

∙ Biodiversity hot spots= smaller areas with lots of  diversity

Restoration ecology restoring ecosystems too far  degraded 

∙ Bioremediation: using plants, fungi,  prokaryotes etc. to detoxify an area

∙ Biological augmentation: use organisms to add compounds to ecosystem

BSC 116: Final Pre-Test Questions 

∙ Ions move in the direction opposite to that favored by the chemical  concentration gradient when _____.

o they are pumped by proteins that require ATP hydrolysis and when  the electrical charge gradient repulses or attracts them 

∙ Choose the set that includes the most charged compounds that are more  abundant inside neurons, in the cytosol, than outside the neurons, in the  extracellular fluid.

o potassium ions and proteins 

∙ The simultaneous arrival of graded depolarization and a graded  hyperpolarization of equal but opposite magnitude at a particular location  on the dendritic membrane is likely to _____.

o cancel each other out, making it appear as if there was no change  in membrane potential 

∙ In a neuron, during the depolarization phase that may trigger an action  potential _____.

o some voltage­gated sodium channels are open 

∙ Of these choices, neuronal communication between the brain and the  muscles of the leg is best conceptualized as _____. 

o electrical and chemical signaling 

∙ The plasma membrane of a neuron has voltage­gated sodium and  potassium channels. What is the effect of membrane depolarization on  these channels? 

o Membrane depolarization first opens sodium channels and then  opens potassium channels. 

 Membrane depolarization opens both types of channels, but  they respond independently and sequentially. Sodium  

channels open first, initiating the action potential. As the  

action potential proceeds, the sodium channels become  

inactivated and remain inactivated until after the membrane  returns to the resting potential and the channels close.  

Potassium channels open more slowly than sodium  

channels but remain open and functional throughout the  

action potential. 

∙ If the membrane potential of a neuron decreases, the membrane potential  _____. 

o becomes less negative. 

 When the membrane potential of a neuron decreases, the  negative value of the electrical potential across the plasma  membrane is reduced and the membrane potential becomes more positive. 

∙ The fundamental excitable cell in the nervous system is the _____.

o neuron 

∙ The central canal of the spinal cord and the ventricles of the human brain  contain a filtrate of the blood, called _____.

o cerebrospinal fluid 

∙ As vertebrates evolved, the increasingly complex structure of the brain  conferred increasingly complex function, especially apparent in the _____. o cerebral cortex, which is greatly expanded in humans, other  primates, and cetaceans 

∙ Dolphins can be awake and asleep at the same time because _____. o one side of the brain can sleep while the other side maintains  swimming and breathing behaviors 

∙ Emotion, motivation, olfaction, behavior, and memory, in humans, are  mediated by the _____. 

o limbic system 

∙ Motor cortex and somatosensory cortex are _____. 

o organized in similar manner adjacent to each other, and are  anatomically similar from one person to the next 

 The sensory and motor parts of these cortices are  

topographically matched along the border of the frontal and  parietal lobes, and are predictably arranged. 

∙ In adult humans, short­term memory relies on connections in the _____  whereas long­term memories appear to be based in the _____. o hippocampus ... cerebral cortex 

∙ Addiction onset by cocaine and amphetamines is characterized by  increased _____. 

o persistence of dopamine in the brain's synapses 

∙ Parkinsonism is characterized by the loss of _____. 

o dopaminergic neurons 

∙ A thermosensory neuron in the skin converts heat energy to nerve  impulses via a conversion called _____. 

o sensory transduction 

 The conversion of sensory energy to a change in membrane  potential is sensory transduction. 

∙ Sensory transduction in the auditory system is much like transduction of  _____. 

o mechanosensory stimuli 

∙ When light first enters the human eye, the first structure that it must pass  through is the _____.

o cornea 

∙ Sensory adaptation is apparent when _____. 

o a person is no longer aware of a heavy necklace that was put on  earlier in the day

∙ The energy for sensory transduction by the lateral line system in fish  comes from _____. 

o water movements 

∙ Rods and cones are similar in that they both _____. 

o release glutamate as the primary neurotransmitter 

∙ The visual information used by honeybees includes these elements that  are not apparent to humans. 

o the ability to distinguish ultraviolet radiation and 300 flashes of light  per second 

∙ The sense described as umami is one of _____. 

o savory and delicious sensation on the tongue 

∙ Myosin heads have binding sites for _____. 

o ATP and actin 

∙ Among these choices, the most energy­efficient form of animal movement, per kg of body mass, is _____. 

o swimming by large fish 

∙ An unlearned behavior directly linked to a stimulus that is carried to  completion once initiated and is essentially unchangeable is _____. o a fixed action pattern 

∙ A learning process that can occur only during a limited period of the  individual's development is called _____.

o Imprinting 

∙ Every morning a graduate student turns on the light in the laboratory and  then feeds the fish in the aquarium. After a couple of weeks of this routine, the graduate student notices that the fish come to the surface to feed as  soon as the lights are turned on. The behavior of the fish is a result of  _____. 

o classical conditioning 

∙ An individual organism has the option to raise various offspring and/or  genetic relatives. Which of the following options represents the greatest  genetic success? 

o one offspring, one nephew, and two grandchildren 

 The coefficient of relatedness between parent and offspring  is 0.5, the coefficient of relatedness between an individual  and a nephew is 0.25, and the coefficient of relatedness  

between grandparent and grandchild is 0.25. This gives a  

coefficient of relatedness of 0.5 + 0.25 + 0.25 + 0.25 = 1.25. ∙ You observe a large black bird with a shiny black crest engaging in  courtship behavior with a little brown bird. It would be reasonable to  hypothesize that this is an example of _____. 

o polygamy

 Both polygynous and polyandrous species tend to be  

sexually dimorphic. 

∙ Which of the following causes Earth's seasons? 

o Earth's tilt on its axis 

∙ Which of the following investigations is an example of the study of an  abiotic factor?

o investigating how the amount of annual precipitation affects the  distribution of a tree species 

∙ In most cases, the two major climatic factors affecting the distribution of  organisms in terrestrial ecosystems are _____. 

o water and temperature 

∙ What is a biome? 

o a major type of ecosystem 

 A biome is a type of community with certain abiotic  

environmental conditions. 

∙ What are the most abundant animals found in the pelagic zone? o What are the most abundant animals found in the pelagic zone?  Zooplankton that graze on phytoplankton are the most  

abundant life­forms in the open ocean of the pelagic zone. 

∙ To determine the density of a rabbit population, you would need to know  the number of rabbits and _____. 

o the size of the area in which they live 

 Density is the number of individuals of population per unit  area. 

∙ In wild populations, individuals most often show a _____ pattern of  dispersion. 

o clumped 

 Individuals are often found clumped because they are  

interacting or are attracted to areas that provide the most  

favorable environmental conditions. 

∙ Which of the following conditions favors "big­bang" reproduction? o low rates of offspring survival 

 If the probability of any one offspring surviving is low, then  parental fitness is enhanced by maximizing offspring  

production. 

∙ In the models that describe population growth, r stands for _____. o per capita population growth rate 

 The growth rate of a population is represented by r, which is  equal to per capita birth rate minus per capita death rate. 

∙ The number of individuals that a particular habitat can support with no  degradation of that habitat is called _____ 

o carrying capacity

∙ According to the principle of competitive exclusion, two species cannot  continue to occupy the same _____.

o ecological niche 

∙ The term used to describe a harmless organism resembling a harmful one is _____. 

o Batesian mimicry 

∙ Cellulose­digesting microorganisms live in the guts of termites and  ruminant mammals. The microorganisms have a home and food, and their hosts gain more nutrition from their meals. This relationship is an example  of _____. 

o mutualism 

∙ An organism's "trophic level" refers to _____. 

o its food source 

∙ Keystone species are those species _____. 

o whose absence would cause major disruption in a community ∙ Which of the following best illustrates ecological succession? o Grass grows on a sand dune, is replaced by shrubs, and then by  trees. 

∙ Caribbean coral reef communities have been strongly influenced by an  unknown pathogen that causes white­band disease. How can the effect of  white­band disease best be described? 

o a cascade event that shifts the entire makeup of the community ∙ On a global scale, energy _____ ecosystems whereas chemical elements  _____ ecosystems. 

o flows through ... are recycled in 

∙ Consider this segment of a food web: Snails and grasshoppers eat pepper plants; spiders eat grasshoppers; shrews eat snails and spiders; owls eat  shrews. The shrew occupies the trophic level(s) of _____.

o secondary and tertiary consumers 

 When shrews eat snails (that eat pepper plants), they are  secondary consumers. When shrews eat spiders (that eat  

grasshoppers), they are tertiary consumers. 

∙ The producers in aquatic ecosystems include organisms in which of the  following groups?

o Cyanobacteria, algae, plants, photoautrotrophs 

∙ Why is a diagram of energy flow from trophic level to trophic level shaped  like a pyramid? 

o Most energy at each level is lost, leaving little for the next. ∙ Biogeochemical cycles are crucial to ecosystem function because _____. o nutrients and other life­sustaining molecules are in limited supply  and must be continually recycled

∙ An ecosystem is unlikely to be limited by the supply of _____ because it is obtained from the air. 

o carbon 

 Atmospheric carbon, in the form of CO2, is incorporated into  living systems by photosynthesis. 

∙ In contrast to bioremediation, which is a strategy for _____, biological  augmentation _____ a degraded ecosystem. 

o removing harmful substances...uses organisms to add essential  materials to 

∙ Which of the following organisms was/were introduced by humans into the United States or its territories?

o European starling, brown tree snake, kudzu, zebra mussels ∙ The single greatest current threat to biodiversity is _____. o habitat destruction 

∙ Which of the following is associated with the small­population approach to  species conservation? 

o Exctinction vortex, mvp, effective population size 

∙ The estimated density or number of individuals needed for a species to  maintain or increase its numbers in a region is the _____.

o minimum viable population (MVP) 

∙ Hot spots are usually chosen for nature preserves because they _____. o save habitat for threatened and endangered species 

∙ Edge species _____. 

o may require conditions found in both of the bordering ecosystems ∙ Which of the following statements best describes why ecologists are  currently concerned with global warming and the thawing of permafrost in  many areas of the tundra biome? 

o The bacterial decomposition of thawed organic materials over the  widespread areas of the tundra will produce large quantities of CO2, which will add to greenhouse gases and exacerbate global  warming. 

∙ The effort to develop, manage, and conserve Earth's resources to meet  the needs of people today without limiting the ability of future generations  to meet their needs is called _____.

o sustainable development

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