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IB HL biology > (option) Neurobiology and Behavior > Flashcards

(option) Neurobiology and Behavior Flashcards

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1
Q

What is a neuron?

A
  • Neurons transmit electrical impulses throughout the nervous system
  • 85 billion in the human NS
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2
Q

What are the three roles of neurons?

A

sensory, relay & motor

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3
Q

What are the three basic components of a neuron?

A

Dendrites – Short-branched fibers that convert chemical information from other neurons or receptor cells into electrical signals

Axon – An elongated fibre that transmits electrical signals to terminal regions for communication with other neurons or effectors

Soma – A cell body containing the nucleus and organelles, where essential metabolic processes occur to maintain cell survival

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4
Q

What is the purpose of the myelin sheath in neurons?

A

The myelin insulates the neuron and allows electrical impulses to pass very quickly.

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5
Q

Neurons generate and conduct electrical signals by pumping what across their membrane?

A

Na+ and K+

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6
Q

What is a membrane potential?

A

The unequal distribution of ions on different sides of the membrane creates a charge difference called the membrane potential

-70

ready to fire

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7
Q

In a typical resting position, what is the charge of a neuron?

A

Inside is more negative (approximately –70 mV)

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8
Q

How is the resting potential of a neuron maintained?

A

Sodium-pottasium pumps ( transmembrane protein) which require ATP

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9
Q

How does a sodium-potassium pump work?

A
  • It expels 3 Na+ ions for every 2 K+ ions admitted (additionally, some K+ ions will then leak back out of the cell)
  • This creates an electrochemical gradient whereby the cell interior is relatively negative compared to the extracellular environment (as there are more positively charged ions outside of the cell and more negatively charged ions inside the cell)

-The exchange of sodium and potassium ions requires the hydrolysis of ATP (it is an energy-dependent process)

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10
Q

What is an action potential?

A

Action potentials are the rapid changes in charge across the membrane that occur when a neuron is firing

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11
Q

What are the four main stages of an action potential?

A

resting potential, depolarization, repolarization and a refractory period

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12
Q

Depolarization
-what is it?
-what happens?

A

-70 → 30
Sodium in
via Sodium channel
In response to a signal initiated at a dendrite

Depolarization refers to a sudden change in membrane potential

As Na+ ions are more concentrated outside of the neuron, the opening of sodium channels causes a passive influx of sodium

The influx of sodium causes the membrane potential to become more positive (depolarisation)

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13
Q

Repolarization
-what is it?
-what happens?

A

30 → - 80
Potassium out
via Pottasium channel

Restoration of a membrane potential following depolarisation.

Following an influx of sodium, potassium channels open within the membrane of the axon

As K+ ions are more concentrated inside the neuron, opening potassium channels causes a passive efflux of potassium

The efflux of potassium causes the membrane potential to return to a more negative internal differential (repolarisation)

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14
Q

Refractory period
-what is it?
-what happens?

A

The refractory period refers to the period of time following a nerve impulse before the neuron is able to fire again

In a normal resting state, sodium ions are predominantly outside the neuron and potassium ions mainly inside (resting potential)

Following depolarization (sodium influx) and repolarisation (potassium efflux), this ionic distribution is largely reversed

Before a neuron can fire again, the resting potential must be restored via the sodium-potassium pump which requires ATP

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15
Q

What are nerve impulses?

A

Nerve impulses are action potentials that move along the length of an axon as a wave of depolarisation and repolitization

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16
Q

The ion channels that occupy the length of the axon are voltage-gated. What does this mean?

A

The depolarization in one segment of an axon triggers the next section to open ion channels to depolarize and therefore the impulse travels across the body of the axon.

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17
Q

What is myelin produced by?

A

Schwann cells

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18
Q

Pros and Cons of myelination of axons

A

The advantage of myelination is that it improves the speed of electrical transmission via saltatory conduction

The disadvantage of myelination is that it takes up significant space within an enclosed environment

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19
Q

Neurons transmit information across synapses by…?

A

converting the electrical signal into a chemical signal

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20
Q

Explain the chemical transfer across synapses

A

1) Action potential arrives at axon terminal
2) Voltage-gated CA2+ channels open
3) CA2+ enters presynaptic neuron
4) CA2+ signals to neurotransmitter vesicles
5) Neurotransmitters move to the membrane and dock
6) Neurotransmitters released by exocytosis
7) Neurotransmitters bind to receptors
8) Signal initiated in post-synaptic cell

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21
Q

What are neurotransmitters?

A

chemical messengers released from neurons that transmit signals across the synapse

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22
Q

What do neurotransmitters do?

A
  • Neurotransmitters are released in response to the depolarisation of the axon terminal of a presynaptic neuron
  • Neurotransmitters bind to receptors on post-synaptic cells and can either trigger (excitatory) or prevent (inhibitory) a response
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23
Q

What is an example of a neurotransmitter?

A

acetylcholine

It is commonly released at neuromuscular junctions and binds to receptors on muscle fibres to trigger muscle contraction

It is also commonly released within the autonomic nervous system to promote parasympathetic responses (‘rest and digest’)

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24
Q

What does acetylcholine do

A

-Plays a role in brain functions, such as memory, and body functions, such as muscle contractions to move your muscles Produced in pre-synaptic neuron by combining choline with acetyl group obtained from cellular respiration

  • Acetylcholine binds to receptors in post-synaptic membrane and only remains bound there for a short time
  • Acetylcholinesterase is present in the synaptic cleft and rapidly breaks down ac
  • Choline reabsorbed and recombined with acetyl
  • Action of neonicotinoids in insects: bind to acetylcholine receptors and thus block acetylcholine and paralyze insects
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25
Q

What do neonicitanoids do

A

Bind to acetylcholine receptors and thus block acetylcholine and paralyze insects

Insects have a different composition of acetylcholine receptors which bind to neonicotinoids much more strongly
Hence, neonicotinoids are significantly more toxic to insects than mammals, making them a highly effective pesticide

Bad for bees

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26
Q

Channels opened by excitatory vs inhibitory neurotransmitters and the polarization created

A

Excitatory neurotransmitters = depolarisation by opening sodium or calcium channels

Inhibitory neurotransmitters = hyperpolarisation by opening potassium or chlorine channels

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27
Q

For a typical neuron, the threshold potential (required to open voltage-gated ion channels) is approximately…..

A

–55 mV

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28
Q

The neural tube of embryonic chordates is formed by….

A

infolding of ectoderm followed by elongation of the tube

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29
Q

Neurons are initially produced by _______ in the _______________.

A

differentiation
neural tube

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30
Q

Immature neurons do what?

A

migrate to a final location

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31
Q

An axon grows from each immature neuron in response to…..

A

chemical stimuli

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32
Q

Some axons extend beyond the neural tube to reach….

A

other parts of the body

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33
Q

A developing neuron forms multiple…..

A

synapses

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34
Q

What happens to synapses that are not being used?

A

Synapses that are not used do not persist. This is called neural pruning

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35
Q

Neural pruning involves the loss of….

A

unused neurons

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36
Q

The plasticity of the nervous system allows….

A

it to change with experience

37
Q

What is spina bifida? What causes it?

A

When the neural tube doesn’t close properly in early development. This can cause physical and mental disabilities

more detail…

It is most commonly seen in the lumbar and sacral areas, as these are the regions where closure is slowest.

The vertebral processes do not fuse, leaving the spinal cord nerves exposed and prone to damage

Spina bifida is believed to be caused by a combination of genetic and environmental factors. The average worldwide incidence of the condition is ~1 in 1,000 births. Not having enough folate in the diet during pregnancy is believed to play a significant role in causing spina bifida

38
Q

How does the neural tube form?

A
  • Three layers of tissue develop in an embryo: ectoderm, mesoderm, and endoderm
  • Neural plate develops from cells in the ectoderm, then folds inward (neural groove), then separates from the ectoderm and seals to form the neural tube
39
Q

Neural migration may occur via one of two distinct processes. Talk about them.

A

glial guidance or somal translocation

glial guidance: Glial cells may provide a scaffolding network along which an immature neuron can be directed to its final location

somal translocation: the neuron may form an extension at the cell’s perimeter and then translocate its soma along this length

40
Q

What is a stroke?

A

A stroke is the sudden death of brain cells in a localised area due to inadequate blood flow

This results in the improper functioning of the brain, due to the loss of neural connections in the affected area

41
Q

Neuron development

A
  • The billions of neurons in the CNS can be traced back to early stages of development of the neural tube
  • Cell proliferation (mitosis) and differentiation occur throughout embryonic development, but most cell division stops before birth
  • Immature neurons migrate to their final location in the CNS through contractile actin filaments
  • Axons grow from immature neurons in response to chemical stimuli
  • Only 1 axon per neuron, but can have many branches
42
Q

Axon growth

A
  • Axons start in the CNS, but then can grow to be quite long and reach more than 1 meter in humans
  • If the axon is damaged, but cell body remains intact, the neuron can regrow, but some connections may be lost
43
Q

How many synapses for each neuron and where do they synapses occur?

A
  • Neurons can form synapses with other neurons or with muscle or gland cells
  • A neuron can have as few as 2 synapses or as many as hundreds in the brain
44
Q

Plasticity throughout lifespan

A

Plasticity is very high in young children’s brains, but there is some plasticity in adult brains too

45
Q

Parts of the Brain

A
  • Medulla oblongata: controls involuntary activities: swallowing, digesting, vomiting, breathing, heart activity
  • Cerebellum: unconscious functions, like movement and balance
  • Hypothalamus: homeostasis, coordinates nervous and endocrine, secretes hormones to posterior pituitary and regulates anterior pituitary
  • Pituitary gland: posterior lobe stores + releases hormones from hypothalamus and anterior lobe, hormones regulate many body functions
  • Cerebral hemispheres: integrating center for complex functions such as learning, memory, and emotions
46
Q

How do we know the parts of the brain?

A
  • Animal experiments: part of skull removed, animal kept conscious, different parts of brain probed and responses observed (also can occur during human brain surgeries)
  • Lesions: damaged parts of the brain from strokes, accidents, can indicate location of function. Lesions in Broca’s area can cause inability to speak.
  • Autopsy post-mortem
  • Functional magnetic resonance imaging (fMRI). Can detect which regions of brain get blood flow when subject receives various stimuli
47
Q

Pupil Reflex

A
  • When bright light is shined into one eye, the pupils of both eyes constrict which indicates that the medulla oblongata is still functioning
  • No pupil reflex indicates “brain death”
48
Q

How do we know that the medulla oblongata is functioning?

A
  • When bright light is shined into one eye, the pupils of both eyes constrict
  • Patients in comas can often recover from damage to cerebral hemispheres, but damage to medulla oblongata is more serious
49
Q

Unconscious Coordination is from __________

A
  • Autonomic nervous system
50
Q

Two parts of the Autonomic nervous system

A
  • Two parts: parasympathetic and sympathetic act in opposite ways
  • Parasympathetic: heart rate slows, less blood flow needed to heart, increased blood flow to gut, pupil constricts to protect retina
  • Sympathetic: heart rate speeds up, more blood pumped, less blood flow to gut, pupil dilates to give better image
51
Q

The Cerebral Cortex

A
  • Forms a larger proportion of the brain and is more highly developed in humans than in other animals
  • Human cerebral cortex has become enlarged through extensive folding that provides increased surface area
  • Cerebral hemispheres are responsible for higher order functions
  • Left cerebral hemisphere receives sensory input from receptors in the right side of the body and vice versa
  • Human brain metabolism requires large energy inputs (over 20% of basal metabolism)
  • Special areas: visual cortex in each hemisphere, nucleus accumbens (pleasure centers) in each hemisphere, and Broca’s area (speech) in the left hemisphere
52
Q

4 Human Sensory Receptors

A
  • Mechanoreceptors: can sense mechanical energy in the form of sound waves, and movements due to pressure or gravity
  • Chemoreceptors: chemicals dissolved in water (taste) or chemical substances in the air (smell)
  • Thermoreceptors: temperature changes detected by nerve endings
  • Photoreceptors: electromagnetic radiation, usually visible light, detected by rods and cones on the retina
53
Q

Olfactory receptors

A
  • Olfactory receptors in the epithelium of the upper inside of the nose
  • Cells have cilia that extend into air of the nose and have odorant receptor molecules on them
  • Many different receptors for different smells!
  • Some animals have over a 1000 different receptors, like mice. Humans have about 400! But can detect billions of odors!
  • Most animals can distinguish a large number of chemicals in the air (and even in the water)
  • Human sense of smell is insensitive and imprecise compared to other animals
54
Q

The Human Ear parts

A
  • Outer ear: pinna
  • Middle ear: ear drum (tympanic membrane), 3 bones or ossicles (malleus, incus, stapes)
  • eardrum picks up sound waves and transmits to bones of middle ear
  • bones amplify sound, act as levers, transfer sound to oval window. Oval window transfers sound to inner ear
  • Inner ear: Oval window transfers sound waves to fluid filling of cochlea
  • Semicircular canals: 3 fluid-filled tubes used for balance. Hair cells in the canals detect movement of the head
55
Q

Cochlea

A
  • spiral-shaped tube with receptors called hair cells
  • hairs vibrate at different frequencies through resonance
  • when they vibrate, they send messages across synapses and on to the brain via the auditory nerve
  • Sound exits the cochlea through the round window
  • In the brain, sound is primarily processed in the sensory cortex (at top of temporal lobe)
56
Q

Cochlear Implants

A
  • Hearing aids can amplify sounds to help people hear better, but if hair cells are defective they don’t help
  • Cochlear implants can help as long as the auditory nerve is still functional
  • External parts are a microphone, speech processor, and transmitter that sends signal to internal parts
  • Internal parts include a receiver, a stimulator that converts signals into electrical impulses, and electrodes to stimulate the auditory nerve directly via the cochlea
  • Early cochlear implants made in 1970’s and the technology just gets better and better
  • Don’t give people with profound deafness normal hearing, but improve it quite a bit
57
Q

Eye Parts

A
  • cornea: clear extension of sclera (does most of the refracting)
  • conjunctiva (layer on top of cornea)
  • aqueous humour: watery fluid between lens and cornea
  • vitreous humour: jelly-like fluid in main compartment of eye
  • Iris: colored part, dilates and contracts
  • pupil: hole in middle of iris
  • lens: behind iris, bends light, adjusts for near and far
  • sclera: tough white outer coating
  • choroid: pigmented layer between sclera and retina
  • retina: inner layer of back of eye, contains light sensitive cells (thin!)
  • fovea: depression in middle of back of eye w/ high concentration of cones
  • optic disk (blind spot): place on retina where optic nerve connects
  • optic nerve: sends messages to brain
58
Q

Photoreceptors- rods vs cones

A
  • rods more sensitive to light, so function better in the dark
  • rods absorb all colors, so give monochrome (black and white)
  • cones absorb red, blue, or green, so give color vision
  • up to 200 rods share same sensory neuron, but cones have only 1, therefore cones give higher resolution
  • rod cells widely dispersed on retina, but cones concentrated in center (at the fovea)
59
Q

Structure of the retina

A
  • Going from back wall of eye and forward (towards the light)
  • Pigmented cells (usually dark) (epithelial)
  • Photosensitive cells (thinner rods and thicker cones)
  • Bipolar neurons (inhibited by neurotransmitter when rods and cones are NOT stimulated-kind of backwards, huh?)
  • Bipolar neurons pass impulse to ganglion cells, which have long axons that bring message to brain
  • Axons of ganglion cells pass across the front of the retina and form a bundle at the “blind spot” where they leave the eye as the optic nerve
60
Q

Contralateral processing

A
  • Due to optic chiasm where right brain processes info from left visual field and vice versa. (Note that some axons cross over for same side field and stay on the same side for the opposite side field)
  • Allows for 3-D perception of a flat image
61
Q

Stimulus, Response, Reflex

A
  • Stimulus: an internal or external change in the environment that is detected by a receptor and elicits a response
  • Response: a change in an organism, produced by a stimulus (kind of circular?)
  • Reflex: a rapid unconscious response to a stimulus (does not need brain’s input)
  • Reflex arc: pathway involving at least 2 neurons. An example is when you touch something hot and immediately pull your hand back.
62
Q

Parts of a reflec arc

A
  • receptors: detect stimulus, cells or nerve endings
  • sensory neurons: receive message across synapse and carry to CNS
  • relay neurons: receive message from sensory neuron and pass to motor neuron (exist in CNS)
  • motor neuron: receive message from relay and carry to effector
  • Effector: carries out response, can be muscles or glands
63
Q

Innate Behavior

A
  • Innate behavior originates independently from the environment, learned behavior is a result of experience
  • Innate behavior is passed on genetically
  • Most invertebrates have only innate behavior
  • For example, the flatworm swims towards food

Rate of movement is determined by level of stimulus, but direction is not affected

64
Q

Examples of Learned Behavior and Survival

A
  • Chimpanzees use sticks to probe termite mounds!
  • Birds learn to avoid orange and black cinnabar moths (color and taste)
  • Bird species avoid action when warning calls heard
  • Foxes avoid electric fences
  • Hedgehogs learn to run across roads instead of rolling into ball
65
Q

Pavlov’s Dogs: reflex conditioning

A
  • Dogs salivate when they see or taste food (unconditioned response)
  • Pavlov rang a bell (neutral stimulus) before he presented dogs with food
  • After a few days of doing this, dogs salivated with sound of bell, but with no food present (conditioned response)
  • Dogs learned to associate 2 external stimuli
66
Q

Development of birdsong

A
  • In some species birdsong is both innate and learned
  • Male chaffinches sing to attract females and keep away other males
  • Songs have a particular shape for the species, but also have individual traits
    • Males raised in isolation have song graphs with different shapes than males raised within hearing of other male chaffinches
67
Q

Imprinting and Operant Conditioning

A
  • Imprinting is learning that occurs at a particular life stage and doesn’t depend on the consequences of the behavior
  • The classic case is the goose that attaches to the first large moving object (usually its mother) and then follows it around for the first weeks of life
  • These geese can imprint on animals from different species, including humans, or even inanimate objects
  • Operant conditioning: learning by trial and error essentially
  • Occurs when animal tries out different behavior patterns and depending on results, behavior is reinforced or inhibited
68
Q

Learning and Memory

A
  • Learning is the acquisition of skill or knowledge that occurs over an animal’s lifetime
  • It includes motor skills (walking, talking, playing baseball), as well as knowledge acquisition (learning types of trees, names of presidents, the lines of a play, etc)
  • Learning is a higher order function. Social animals are most likely to learn from each other
  • Memory: the process of encoding, storing, and accessing information
  • Short-term memory lasts about a minute
  • Long-term can last indefinitely
  • Experiences cause new synapses to be formed
  • Role of hippocampus in memory
69
Q

Summation

A

Summation: post-synaptic neurons can receive NT’s from many pre-synaptic neurons and the total effect is added up (summed).
- If total exceeds threshold, then post-neuron will trigger action potential

70
Q

Slow and Fast NT’s

A
  • Fast NT’s pass messages in less than a millisecond using gated ion-channels as receptors (immediate change but brief)
  • Slow-acting NT’s take a lot longer (100’s of ms) and diffuse through surrounding fluid to affect multiple post-synaptic neurons
  • Slow-acting NT’s include norepinephrine, dopamine, and serotonin
  • They don’t affect ion movement directly, but cause the release of secondary messengers that will
  • Slow NT’s act to modulate the faster NT’s. It is slower, but lasts for a longer time
  • Slow-acting NT’s seem to have something to do with promoting memory and learning
71
Q

Neurotransmitters in relation to learning and memory

A
  • Memory and learning involve changes to neurons caused by slow-acting NTs (neuromodulators)
  • These cause the release of secondary messengers inside post-synaptic neurons that can increase number of receptors in post-synaptic or chemical modification of these receptors to increase rate of ion movements once the NT binds
  • Secondary messengers can persist for days and cause long-term potentiation (LTP)
  • Longer term memories are caused by remodeling of synaptic connectionsrt
72
Q

Drugs

A
  • Drug: A chemical that is ingested, injected, or inhaled in order to change functioning of the body.
  • Psychoactive drugs affect the brain and personality. Generally work through altering transmission at synapses.
  • Excitatory (stimulant): cocaine, amphetamine, nicotine, caffeine. Stimulant drugs mimic the stimulation provided by the sympathetic nervous system
  • Inhibitory (sedative): alcohol, tetrahydrocannabinol (THC), and benzodiazepines (valium, paxil, xanax), opiates
73
Q

How do psychoactive drugs work?

A

1) have structure similar to neurotransmitter, so they bind to receptors and prevent usual effect

2) have structure and effect similar to normal neurotransmitter, but don’t break down, so last much longer

3) Interfere with breakdown or reuptake of neurotransmitters, so prolong effect of neurotransmitter

74
Q

Effects of cocaine

A
  • Works at synapses where dopamine is a neurotransmitter
  • Binds to proteins that pump dopamine back into pre-synaptic neuron, thus blocking reabsorption
  • Dopamine remains in synapse leading to prolonged euphoria
  • Cocaine is highly addictive
  • Brain tissue taken post-mortem from cocaine addicts shows lower levels of dopamine
  • Body responds to cocaine by secreting less dopamine, which leads to depression when not using cocaine
  • Crack is a form of cocaine that can be inhaled, which leads to an even more intense effect
75
Q

Effects of THC

A
  • Cannabis contains a number of chemicals, but THC causes most of its psychoactive effects
  • THC binds to cannabinoid receptors and blocks release of an excitatory neurotransmitter (it inhibits)
  • Cannabinoid receptors found in synapses in different parts of the brain, including cerebellum, hippocampus, and cerebral hemispheres
  • Good evidence for psychomotor impairment by THC (don’t drive!), short-term memory impairment, stimulation of appetite and other effects
76
Q

Narcotics (opiates)

A
  • Includes opium, heroin, codeine, fentanyl, morphine, oxycodone, etc
  • Originally come from the poppy plant. Other forms are semi-synthetic or completely synthetic (made in the lab)
  • Depressant drug
  • Very dangerous in causing overdose because opiates bind to receptors in areas of the brain that control breathing and can stop breathing altogether
77
Q

Factors that influence drug addiction

A
  • Dopamine secretion: dopamine makes you feel good, makes it very difficult to stop
  • Genetics: addictions can run in families, genetic predisposition makes people more likely to become addicted, but other factors are needed
  • Social factors: traditions, peer pressure, poverty, trauma, mental health issues
78
Q

Pain

A
  • Pain receptors are located in the skin and other organs, can perceive mechanical, thermal, or chemical stimuli. Send impulse to pain receptors in cerebral cortex, causing feelings of pain
  • Pain helps warn us about potential dangers to our bodies
  • Pain can also distract us from important things.
  • In some cases, pituitary releases endorphins, which bind to receptors in neurons carrying pain signals
79
Q

Impact of MDMA (ecstasy)

A
  • MDMA causes an increase in both serotonin and dopamine release and slows down their reuptake
  • This initial increase in NT’s is followed by a short-term decrease
  • It has stimulant and psychedelic effects
  • MDMA has been associated with some deaths due to increased body temperature and dehydration
80
Q

Anesthetics

A
  • Act by interfering with neural transmission between areas of sensory perception and the CNS, so the “trauma” to your body is still there, but you don’t perceive it
  • Local, cause numbness in a limited part of the body (used for dental work, stitches)
  • General: cause unconsciousness. Used for many surgeries.
  • Some procedures require awareness, so patients are kept partially conscious
  • Epidurals (used for C-section births) are spinal blocks, so patient is conscious but pain sensation can’t go beyond spinal cord
81
Q

Ethology

A
  • Ethology is the study of animal behavior in natural conditions
  • Natural selection can change the frequency of observed animal behavior
  • Behavior that increases the chances of survival and reproduction will become more prevalent in a population
  • Learned behavior can spread through a population or be lost from it more rapidly than innate behavior
82
Q

Evolution of Altruistic Behavior

A
  • Altruism in biology: actions that increase another individual’s lifetime number of offspring at a cost to one’s own survival and reproduction. Parental care NOT altruism.
  • Blood sharing in vampire bats: large groups in Costa Rica feed at night by sucking blood from large animals, bats can die if they fail to feed for 2 consecutive nights, other bats regurgitate blood to feed these bats, even if they are unrelated genetically: reciprocal altruism, may be paid back in the future and benefits whole group
83
Q

Foraging in Shore Crabs

A
  • Shore crabs choose mussels of medium size when presented with mussels of all sizes
  • Medium sized mussels provide the greatest energy return per second of time spent breaking open shells
84
Q

Synchronized Oestrus in Lions

A
  • Female lions stay in their pride, but males are expelled when they are about 3 years old (the Lion King!)
  • Males can only breed if they overcome the dominant male through fighting. 2 related males have a better chance at overcoming a powerful male
  • New male might kill suckling cubs to make females go into oestrus (heat) so they can father their own cubs faster
  • Females fiercely protect their cubs, but will accept new male if he takes over
  • Female lions in a pride have synchronized oestrus so they can suckle each other’s cubs while one is hunting and
  • So their males can leave the pride together and try to take over another pride
85
Q

Blackcap Migration

A
  • Used to only be from Germany south to Spain, but now 10% migrate to the UK. Why?
  • Direction of migration is genetically programmed. When it was colder, birds that flew west to UK couldn’t survive extreme conditions, but with climate change, the “western flyers” are now being selected for.
  • Birds that arrive in UK earlier, can take the best territories
  • Experiments with migrating blackcaps has proven that direction of migration is genetically programmed
86
Q

Blue Tits and Cream

A
  • An example of the development and then loss of learned behavior
  • Blue tits were observed pecking through aluminum foil tops of milk bottles in the 1920’s to drink the cream on top
  • The behavior was soon observed 150 km away!
  • The behavior spread until German occupation stopped delivery of milk for 8 years
  • Within months of return of milk delivery, the behavior started again, proving the behavior was learned rather than innate
  • Recently it has been reported that blue tits don’t drink from bottles anymore. Why?
  • People buy milk at store more often and milk is homogenized or skim
87
Q

Blood Sharing in Vampire Bats

A
  • Female vampire bats live in small colonies of 8-12
  • They feed on about 25 mL of mammalian blood per night
  • They risk starvation if they don’t eat for 2-3 consecutive nights
  • Bats who have fed regurgitate blood for bats who have not
  • This is altruism because it benefits other unrelated bats and has a cost for the giver
  • Why would bats do this?
  • Overall, blood sharing gives more security to the colony
  • The giver of blood on one day may be the receiver on another
88
Q

Breeding Strategies in salmon

A
  • Coho salmon breed in rivers that discharge into Northern Pacific Ocean
  • Adults die after breeding and young live in river for about a year before migrating back to the ocean
  • 2 Breeding strategies: hooknoses fight each other for right to fertilize female eggs
  • Jacks avoid fights and sneak up on females to try to fertilize their eggs
  • Whether a salmon becomes a hooknose or jack depends on growth rate. Faster growing salmon return to river after only 2 years and become jacks
  • Slower growing stay in ocean for an extra year and thus are larger when they do come back (the hooknoses)
  • Remember this as an example of disruptive selection??
89
Q

Courtship Rituals in
Birds of Paradise

A
  • Plumage patterns and courtship dances of male birds of paradise are often quite flashy and exaggerated
  • Females of these species tend to be more drab
  • Why are the males so flashy, even when the traits don’t help in their survival?
  • Females tend to prefer the flashiness
  • Maybe it indicates efficiency in feeding and overall fitness
  • Afterall, a male who can jump around with ridiculous amounts of feathers must be healthy!
  • Over the generations, traits get more and more exaggerated

IB HL biology (12 decks)

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