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Ch. 12 Evolution, Nervous Systems, and Behavior. Our primary sense = vision and we tend to think of this as normal. Other animals may perceive the world.

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Presentation on theme: "Ch. 12 Evolution, Nervous Systems, and Behavior. Our primary sense = vision and we tend to think of this as normal. Other animals may perceive the world."— Presentation transcript:

1 Ch. 12 Evolution, Nervous Systems, and Behavior

2 Our primary sense = vision and we tend to think of this as normal. Other animals may perceive the world very differently. Instead of a world with colors and shapes, it may be made up of odor textures, heat shapes, and electrical fields. Umwelt - an animal’s environment as constructed by its sensory apparatus. This depends on the sensory filtering mechanism of an animal. Ex. Humans vs. ants

3  Nerve structure  Motor, sensory, interneuron Axon synapse Cell body dendrites Sensory receptor Motor neuron CNS Effector organ

4  Nervous system evolution:

5  Brainstem  Hindbrain ▪ Pons + Medulla oblongata ▪ Filters sensory and motor information going from body to forebrain ▪ Regulates sleep patterns ▪ Coordinates movement  Midbrain ▪ Processes auditory input ▪ Filters sensory and motor information going from body to forebrain

6  Cerebellum (Hindbrain) ▪ Controls body movement ▪ Balance and coordination ▪ Learning and remembering motor responses  Forebrain  Cerebrum ▪ Corpus callosum is a thick band of neurons that connect the two hemispheres ▪ Responsible for reasoning, speech (vocalizations), learning and memory, vision and visual association, hearing, smell, taste, body movements, etc.

7  Forebrain con’t  Limbic system ▪ Thalamus – cell bodies of interneurons connecting to the cerebral cortex. Filters and sends input to appropriate area of cortex ▪ Hypothalamus – regulates Pituitary gland via neurosecretory cells ▪ Suprachiasmatic nuclei – biological clock ▪ Hippocampus – memory formation and recall/ navigation ▪ Amygdala – emotional memories

8 Structures –Euglena eyespot ---- vertebrate eye Can consist of light/ dark, color (diff. Wavelengths), polarized light (vibration plane of light that varies with the position of the sun) Planaria Vertebrate eye


10 Functions:  Communication: Octopus color changes communicate emotion states Silverback gorillas Body posture and eyelid flashes in baboons Vervet monkeys in Africa – male genitalia



13  Location of prey/ predators : ex. Strobing in octopus to flush prey; many species  Location and recognition of mate: insects, lizards, fish, birds, mammals; many species

14 Both translate vibrations (airborne or substrate borne) into electrical signals in the nervous system Structures : Ex. Cochlea of mammals with bending hairs Ex. Tactile receptors of star-nosed mole

15 Somatosensory cortex

16 functions: communication speech, ant alarm - stridulation, snake rattle mate recognition and location cricket song - rubbing wings location of prey/predators hear movement - cats maternal recognition Mallard ducks - piping by young in eggs and vocalizations of mother orientation - echolocation (Donald Griffin/ little brown bat in 1950’s)


18 Ex. Taste receptors on tongue Ex. Flehmen in buffalo, deer - male tests female for estrus Dendrite of sensory neuron has receptors for specific molecules. When molecules bind in sufficient numbers, the axon fires.

19 Functions:  Communication - marking territory boundaries with urine or glandular secretions  Mate recognition and location Bombyx mori, male has 17,000 receptors on brush- like antennae  One molecule of female pheromone initiates a nerve impulse in the male - need 200 such nerve impulses to induce male to search for her  Prey/ predator recognition Mussels increase heart rate when exposed to water w/ snail predator

20  Test for food quality – taste  Orientation and migration – salmon  Trail pheromone in ants  Maternal/ kin recognition Newborn sheep learn mother’s odor


22  Ex. Electric fish - Brieomyrus can change frequency of electrical field to avoid jamming from the field of another fish. They use perturbations in their electrical field to locate prey and move about in murky water. Pulse patterns in the electrical field are important in species and potential mate recognition

23  optical illusions


25 = Nervous system selectively receives and processes particular information from the environment. Ex. Of Bats and Moths Summer evening - bats foraging for moths - some captured, some make evasive movements and escape How do the moths know a bat is coming?


27 He then turned on a high frequency sound that drown out the sound of the bats Bats immediately ran into obstructions and fell to the floor, where they stayed until the sound was turned off - lower frequencies did not have the same effect.

28  Conclusion: echolocation - high frequency pulsed sound bounced off surrounding objects - is important for navigation in bats

29 Tympanum = sensory receptor in metathorax - message passed to brain via sensory interneurons - which are thought to be able to decode the information and “make decisions” about the appropriate response. metathorax


31 A1 - sensitive to low-intensity sounds; fires more frequently as the sound increases in intensity - thus a moth can tell if the bat is getting closer. A2 - sensitive to high-intensity sounds only Low intensityHigh intensity Neural activity Stimulus

32 Both fire more frequently in response to pulses of sound than to steady uninterrupted sound. Neural activity Stimulus




36 Moth’s response to bat’s approach modified by input from A2 receptor: Low intensity - moth orients such that input to A1 nerve the same and bat behind - flies away quickly. High intensity - A2 nerves fire and they shut off the central steering mechanism  This results in the moth going into wild gyrations and precipitous fall. Bat can not predict position of moth and misses.

37 Why would this be an adaptive response?

38 1. Brain selectively tunes out certain stimuli => Habituation a. cat (alone in cage) brain waves indicate it hears ticking of metronome behind it. Enter mouse, sound of metronome no longer registers. 2. Prioritized attention to competing stimuli a. feeding versus fleeing predator

39 Related process: Hierarchical cue evaluation – multiple cues may be used by an animal, but they are weighted differently  Occurs in a number of situations from nest construction to navigation during migration Ex. Honeybee memory of foraging sites is hierarchical (Menzel and Erbers) Bees were trained to go to peppermint-scented blue triangles. (odor, color and shape)

40 P O bees P P P P P P P O P = peppermint O = orange bees

41 Brain regulation of behavior is a combination of inhibition and stimulation. Ex. Mating in mantid. These insects are hunters and motionless most of time. Ken Roeder explored the controls on behavior by cutting between different parts of the brain. forebrain Subesophageal ganglion S

42 When a ganglion is separated from the rest - movements in the appendages associated with that ganglion stopped. Moved if ganglion was electrically stimulated.  What does brain do?  Remove forebrain - animal begins doing more than one thing at a time. Walks and grasps - conflicting activity  The forebrain appears to be an inhibitory center - keeps insect doing one action.  If the subesophageal ganglion is damaged, animal does not move at all = a stimulatory center

43 During mating, male often loses head as he approaches female. Forebrain is lost, but not subesophageal ganglion. When male’s inhibitory center lost, mating behavior initiated with grasping and movements. While female eats head with forebrain, male can often achieve mating success (headless).

44  Example: sea slug, Tritonia  Alternating dorsal and ventral flexion  CPG = Network of neurons that regulate fixed motor responses (FAP)  Interplay of excitation and inhibition  Produce stereotypic behavior

45  CPG: Dorsal Ramp interneuron coordinates the complex escape behavior through inhibition and excitatory neural activity.  Most work has been done with invertebrates  A similar system has been worked out for singing in male plainfin midshipman fish

46 Endocrine glands – Hormone – Target organ - Feedback mechanism –

47  Prime an animal to perform a particular behavioral act  evidence: ▪ onset of specific behavior correlates with the onset of hormone secretion ▪ precocious induction of a behavior by hormone application ▪ disappearance of a behavior after removal of the endocrine source of a particular hormone

48 Hormones often have direct effects on the changes in anatomy and behavior at the onset of sexual maturity. Ex. White rats Sexually ready males and females have very different behavior  lordosis and copulatory behavior Parental care differences

49 1. Removed ovaries from one group of females 2. Removed ovaries, but then injected females with estrogen and progesterone 3. Removed testes from one group of males 4. Removed testes, but then gave injections of testosterone

50 First female group no longer goes into lordosis, second group does First male group no longer mounts receptive female, second does Conclusion: Results:

51 Methods: using sexually mature rats 1. removed ovaries and injected with testosterone 2. removed testes and injected with estrogen and progesterone Results: both exhibited no reversal in sexual behavior

52 At Puberty Treatment Newborn females No ovaries Newborn females No ovaries Inject w/testosterone Newborn females No ovaries Inject w/ est + prog Inject with Female hormones lordosis lordosis Inject with Male hormone male behavior Same results with newborn males


54 Similar to Learning a language In this case there is a short interval of nine days around the time of birth when the brain of the developing rat is sensitive to testosterone in the blood. Summary of what happens: Males = XY, Females = XX; Y causes testosterone to be secreted by gonads at about 16 days development. If this happens development of ovaries is inhibited. Testosterone enters the blood stream and bind specifically with certain special cells in the brain. The hormone affects the genetic activity of these nerve cells  biochemical activity changes  cell development and connections change. Thus at birth male and females are primed to be responsive to certain hormones. Later with exposure to these hormones, sexual behavior is exhibited.

55 Ex. Anolis behavior (David Crews)  Females and males go through seasonal changes in behavior  Hormones produced by the ovaries regulate the onset of sexual receptivity  (injection with hormones will trigger immediate onset of sexual receptivity)  Females do not respond to these hormones if they are captured and treated in the fall  (when they normally enter dormancy)

56  They respond to hormones in late spring and early summer only  ( temperature cues are important – warming temperatures)  Social environment is important – seeing displaying male causes more rapid ovary dev.  (female receptivity triggered by displaying male is also shown in doves and other animals)

57  female ovulation is limited to summer (appropriate) and when males available  female produces large, nutrient rich egg and carrying it around may slow her down  a female will survive and reproduce more successfully if she carries an egg only when appropriate.  A female stimulated by a displaying male will make it more likely that she mates with a dominant and strong territorial male.

58 Ex. Labrides dimidiatus (marine wrasse fish)  Males defend large territories with 3-6 females nesting in it. Females ranked in a linear dominance hierarchy  If dominant male dies, largest female becomes male territorial holder  Within a few hours – behavior changes are induced by hormonal changes  Male spawning behavior appears in 2-4 days  First sperm produced within days

59  Social interactions are important in regulating reproductive behavior  Adaptive – female gametes are limiting resource. One male can dominate an area in which 3-6 females live. Females can always mate, no matter what their size. Males can only mate if large and a territorial holder.  However, females are limited to one brood per season, a male is not.  Thus optimum strategy – be female when small, male when large

60 Ex. Polistes fuscatus (common paper wasp)  Females initiating a nest form a dominance hierarchy – all are fertilized reproductives  Dominant female aggression affects juvenile hormone levels in subordinates and their ovaries regress – become sterile workers

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