W6: Vertebrate Physiology (Homeostasis & Phenotypic Plasticity) [Dr. Matt] Flashcards
Responses of animals to environmental changes: what are the changes that animals would need to respond to? (3)
- Acute (short-term) changes in individuals.
- Chronic (long-term) changes in individuals.
- Evolutionary changes in population traits via NS.
Response of animals to acute changes?
Homeostasis.
Response of animals to chronic changes?
Phenotypic plasticity.
Responses of animals to evolutionary changes?
Genetic adaptation (over generations).
Homeostasis?
= processes to maintain fairly stable conditions in the body.
Phenotypic plasticity?
= the ability of a genotype to produce multiple phenotypes.
Egs of Phenotypic plasticity? (2)
- Acclimatisation.
- Acclimation.
Strategies of responding to the external environment? (3)
- Regulation.
- Conformity.
- Mixed conformity & regulation.
Regulation?
= when an animal’s internal environment is held constant when its external environment changes.
Conformity?
= when an animal’s internal environment varies so that it matches the external environment.
Mixed conformity & regulation?
= when an animal’s internal environment either remains constant or varies to match the external environment for different conditions.
Eg of Mixed conformity & regulation?
Salmon.
Explain the Salmon eg? (2)
- These salmon are temperature conformers, as their internal environment matches the temperature of the water that they are in (river or ocean water).
- These salmon are also blood concentration regulators, as their internal environment remains constant irrespective of the salt concentration of the water.
Types of feedback systems? (2)
- Negative feedback.
- Positive feedback.
Negative feedback attributes? (5)
- Regulatory processes that maintain homeostasis.
- Sensors continuously sample controlled variables (eg, temperature, pH).
- Deviations from setpoints stimulate immediate corrective measure.
- Respond using physiological, biochemical, behavioural or other mechanisms.
- Opposes deviation to bring the variable back to the setpoint.
Egs of negative feedback systems? (3)
- Regulation of blood glucose levels.
- Regulation of CO2 levels.
- Regulation to changing temperatures.
Regulation of blood glucose levels? (11)
1) If the blood glucose level rises:
- Beta cells in pancreas secrete insulin into the blood.
- Body cells take up glucose.
- Liver takes up glucose & stores it as glycogen.
- Blood glucose level declines.
- Homeostasis.
2) If the blood glucose level declines:
- Alpha cells in the pancreas secrete glucagon.
- Liver breaks down glucagon & releases glucose.
- Blood glucose level rises.
- Homeostasis.
Regulation of CO2 levels? (11)
- Physical activity increases.
- Cellular respiration increases.
- CO2 production increases.
- Medulla oblongata stimulated.
- Impulses sent to the heart & lungs.
- Heart rate increases.
- Blood with CO2 brought faster to the lungs.
- Breathing rate increases.
- CO2 exhaled more rapidly.
- CO2 level drops.
- Normal CO2 level.
Regulation to changing temperatures? (14)
1) Brain signals to skin via nerves that it’s Too cold (low temperatures):
- Vasoconstriction, shivering & MR rising.
- Response = heat conservation/production.
- Blood temperature rises.
- “Homeostasis”.
2) Brain signals to skin via nerves that it’s Too hot (high temperatures):
- Vasodilation & sweating.
- Response: heat dissipation.
- Blood temperature drops.
- Homeostasis.
Positive feedback attributes? (3)
- Amplifies changes, not stabilises.
- Accelerates processes & initiates changes.
- Less common in homeostasis.
Eg of positive feedback?
Childbirth.
Childbirth? (7)
- Head of baby pushes against the cervix.
- Nerve impulses from cervix transmitted to brain.
- Brain stimulates the pituitary gland to secrete oxytocin.
- Oxytocin is carried in the bloodstream to the uterus.
- Oxytocin stimulates uterine contractions & pushes bay towards the cervix.
- Process is repeated until the baby is delivered.
- It’s a continuous process (amplifies).
Recap: Homeostasis & feedback systems? (3)
- Homeostasis.
- Regulation vs conformity in animals (can be intermediate & mixed responses for different conditions).
- Negative feedback regulatory systems.
Dynamic equilibrium in homeostasis attributes? (3)
- Balanced state in systems.
- Conditions fluctuate within an acceptable range.
- Tied to circadian rhythms.
Egs/Instances of circadian rhythms? (2)
- Human body temperature fluctuates throughout the day around the setpoint value.
- Fever responses to infection.
Brief explanation of fever response to infection? (5)
- Normal thermoregulation before fever (37C).
- Set point rises & shivering and vasoconstriction is activated.
- Regulation of body temperature at the elevated level during fever (40C).
- As the setpoint returns to normal, sweating & vasodilation are activated.
- Normal thermoregulation after fever.
Egs of the sickness behaviours? (4)
- Fever.
- Lethargy (fatigue).
- Sleepiness.
- Social withdrawal.
Fever instances? (2)
- Fever in a kudu.
- Fever in vervet monkeys.
Fever in a kudu?
Shows the changes in body temperature in a kudu with fever (febrile) and one without fever (afebrile).
Fever in vervet monkeys? (2)
- It was observed that vervet monkeys with fever had temperature spikes caused by a fever, indicated by a sustained upward shift in body temperature, & hyperthermia, indicated by a single spike in temperature due to it being very hot that day.
- Vervet monkeys with fevers were more agressive & frequently fought with other monkeys, but get severely injured in the fights. Therefore, they would have to trade-off between fighting or getting injured.
Recap: Dynamic equilibrium & fever? (2)
- Dynamic equilibrium in homeostasis.
- Fever responses to infection (elevated Tb temp. setpoints, associated sickness behaviours & trade-offs in wild animals).
Genotype?
= genetic make-up of an organism.
Genotype attributes? (2)
- Inherited, DNA-coded information.
- Determines a trait/group of traits.
Phenotype?
= observable characteristics of an organism.
Phenotype attributes? (2)
- Pattern of gene expression.
- Influenced by genotype & environment.
Phenotypic plasticity attributes? (5)
- Adaptive responses within an individual to different environmental conditions.
- Changes in behavioural, physiological, morphological & life-history traits.
- Increases fitness & survival.
- Controlled by homeorhetic processes.
- Functions to maintain a form of balance between transitional periods.
Categories of phenotypic plasticity? (2)
- Phenotypic flexibility.
- Development plasticity.
Phenotypic flexibility?
= reversible adjustments within individuals in response to environmental changes.
Phenotypic flexibility attributes? (3)
- Can occur throughout an individual’s life.
- Allow an animal to maintain/enhance performance in environments that have rapid fluctuations in conditions.
- Acclimatisation vs acclimation.
Acclimatisaton VS Acclimation?
- Acclimatisation
= response to natural changes in the environment. - Acclimation
= response to artificial changes in the environment (eg, in a lab).
Egs of Phenotypic flexibility? (2)
- Thermal acclimation in rodents in response to cold environments.
- Marine iguanas.
Explain thermal acclimation in rodents in response to cold environments?
Marine iguanas? (2)
- Variations in body size in relation to food availability.
- Smaller iguanas (more flexible ones) are more likely to survive than those who don’t change their body size/length (bigger ones), as they are able to adapt to food shortages.
Development plasticity?
= phenotypic changes during the developmental stages of an individual’s life in response to environmental conditions.
Development plasticity attributes? (2)
- Changes are not reversible after developmental stages.
- There are physiological trade-offs involved.
What physiological trade-offs are involved in development plasticity? (2)
- Adaptive during developmental stages.
- May lead to negative fitness consequences later in life.
Egs of Development plasticity? (2)
- Hokkaido salamander.
- Zebra finches.
Hokkaido salamander?
Typical morph developed a deeper tail in the presence to a predator threat than in the absence of predators compared to broad-tailed morphs.
Zebra finches?
Pro of being a small chick in hot conditions are less loss of heat to the environment due to having a small SA (chick size is in response to parent calls to heat).
Recap : Phenotypic plasticity? (2)
- Genotype vs phenotype.
- Phenotypic plasticity (phenotype flexibility & development plasticity).
