Lec 15 slides and reading

Question 1

Physiological ecology as a way of thinking about organisms

Answer 1

Can view an organism a library of information, bearing detailed sets of genetic info written in DNA
Necessary to direct the assembly of a complex organism
It’s heritable and connects that organism to other organisms in a family tree of relatedness

Question 2

How environmental factors determine distribution and abundance

Answer 2

All organisms have restricted spatial distributions
-if environmental factors in a particular habitat are too harsh for a particular species, it won’t be able to persist there

Environmental factors classified in 2 ways: abiotic and biotic factors

Question 3

abiotic and biotic factors

Answer 3

Abiotic factors are manifestations of the non-living, physio-chemical world, whereas biotic factors arise from the actions of other organism

Question 4

abiotic factors divided into:

Answer 4

conditions and resources

Question 5

resources

Answer 5

Resources are necessary physical entities that organisms use up and can be depleted

Question 6

conditions

Answer 6

Conditions are physical states that can’t be depleted, such as temp or pH

Question 7

limiting factors

Answer 7

Factors that are important in determining whether a species can or can’t persist in an area are called limiting factors

At the broadest possible level, the 2 factors that are most likely to limit the distributions of terrestrial species are temp (condition) and water (resource) → considered “the Big 2”

Question 8

why is altitude considered a complex gradient

Answer 8

Altitude considered a complex gradient because many simpler factors vary with altitude in nature: temp, amount of precip, type of precip, partial pressure of oxygen, depth of winter snow

Question 9

Any particular species is likely to be restricted to only a portion of an ecological gradient, if the factor that varies along the gradient is a …

Answer 9

limiting factor

-that portion constitutes the range of tolerance for that particular factor, and it can also be considered as defining part of the niche of that species

-range of tolerance classically graphed as curves that show how an organism’s ability to function changes along the gradient

-if the gradient is long enough, there’s usually a peak at some point, where the environ is optimal for the organism to THRIVE

Question 10

death zones

Answer 10

At increasing distances from their optimum, organisms find the environment increasingly stressful

First, they become unable to grow well enough to reproduce, then they become unable to grow at all and finally they become unable to live → death zones

Question 11

why is water important

Answer 11

Water is important because it affect the concentrations of chemical rxns, but especially because cells and tissue depend on membranes to compartmentalize chemical processes and reactants

Proper functioning depends on osmotic balance
If cells get too dry, the concentrations of dissolved salt increase
Chemical rxn are slowed and changed
If too much water enters cells, rxtnt gets diluted and fail to combine as needed

Question 12

Organisms can also be in danger of overheating, overcooling, drying out and getting waterlogged

Answer 12

Environments typically contain a far broader range of physical conditions than the much narrower ranges of tolerance that characterize organisms (death zones)

Things tend to equilibrate
Objects, whether organisms or inanimate objects like rocks, will tend to reach the same temp as their environ.
In the hot sun, things heat up
In dry environ, objects will lose water and become saltier

Environments are much larger than organisms, so equilibration is asymmetrical
Generally, organisms are intrinsically vulnerable, environments are intrinsically implacable

Question 13

homeostasis

Answer 13

They must be able to keep their internal states constant (or at least within narrow bounds), a process known as homeostasis (“staying the same”)

Question 14

2 categories of homeostasis

Answer 14

thermoregulation (maintaining temp)

osmoregulation (maintaining saltiness)

Question 15

Organisms vary hugely in their capabilities for thermoregulation and osmoregulation
Much of this depends on…

Answer 15

body size and shape

The most important aspect of body structure is the ratio of surface area to volume (SA/V)

Consider a tiny, aquatic, single celled Paramecium in a freshwater pond. Because it is so small, its SA/V ratio is high: any miniscule amount of heat that it could generate in its tiny body would almost instantly be sucked away by the overwhelming mass of water

Question 16

active regulation

Answer 16

refers to the continuous and dynamic process of monitoring, adjusting, and controlling certain conditions, behaviors, or activities to achieve a desired outcome or maintain a specific standard

in biological systems, active regulation refers to how organisms maintain homeostasis (stable internal conditions) despite external changes

For example, the human body actively regulates temperature, blood pressure, and glucose levels
-mechanisms such as sweating, shivering, and the release of insulin are part of active regulation

Question 17

The organisms most capable of homeostasis have _______ bodies and complicated metabolisms

Answer 17

large

warm-blooded animals exhibit very active regulation of heat balance to keep their body temperatures almost constant, despite great fluctuations in ambient temperature

Question 18

cold blooded animals

Answer 18

In contrast, the “cold-blooded” animals (fish, amphibians, reptiles and virtually all invertebrates) tend to be thermoconformers whose body temperatures more closely track ambient temperatures

Question 19

“homeothermy versus poikilothermy”

Answer 19

stresses the constancy of body temperature, as opposed to variability

Question 20

“Endothermy versus ectothermy”

Answer 20

emphasizes that temperature is primarily determined by physiological processes acting within the body, as opposed to being determined by the external environment

Question 21

conduction

Answer 21

Conduction is the direct transfer of heat between two bodies that are in contact
If there is a temperature differential, heat will flow from the warmer object to the cooler
Given enough time, the two objects will equilibrate at the same temperature

Question 22

convection

Answer 22

Convection is heat transfer that is facilitated by a moving fluid—typically air or water. If you stand in an icy flowing stream, the cold water not only extracts heat from your feet in a conduction-like process, but the current sweeps the slightly heated water away, so local equilibration is minimal
Convective flows therefore tend to increase rates of heat transfer
Water is a much more effective medium for heat exchange than air is

Question 23

true or false: radiative heat transfer involves molecules bashing into each other and transmitting their kinetic energy

Answer 23

false

applies only to conduction/convection

Question 24

homeostasis and heat balance

Answer 24

Remember that the active vertebrates we are considering generate considerable amounts of heat from their internal metabolic functions, especially muscle contractions
Shivering is an effective way to increase internal heat production
In a cold environment, animals need to conserve that heat or generate more of it, but in a hot environment, they need to dump it or make less
The most basic adaptations—if not necessarily the most effective—for controlling these balances concern the size and shape of the animals

Question 25

bergmann’s rule

Answer 25

If one examines a number of closely related homeothermic species that occur in habitats with different temperatures, there is a tendency for the species from cold environments to have larger body sizes

Because larger bodies translate to lower SA/V ratios, they retain heat better and lose less of it to their cold surroundings

In a tropical environment, an animal the size of a polar bear would have a hard time shedding heat, and tropical bears are gratifyingly small

Question 26

allen’s rule

Answer 26

He claimed that animals from hotter environments had longer and thinner appendages: legs, tails, ears, sometimes horns or frills
That difference in shape will increase the surface area, given a constant volume
Rabbits are a group in which this trend is nicely shown
The comically large, almost paper-thin ears of rabbits are classic cases of maximizing surface area
Aside from affecting SA/V relationships in purely geometrical ways, extremities can be further specialized for dumping heat from the body core by managing blood circulation

Question 27

how do rabbits follow allen’s rule

Answer 27

Rabbit ears are heavily vascularized, and the flow of blood to them is regulated.
Sphincter muscles around arterioles are especially effective in regulating how much blood is pumped into ears, for example
An overheated rabbit that needs to reduce its body temperature can pump hot blood to the ears, where the large surface area allows quick equilibration
Rabbits can also position their ears to increase or decrease heat exchange

Question 28

Homeothermic vertebrates achieve insulation with…

Answer 28

layers of body fat, or as layers of fur or feathers
In the case of fur and feathers, the real insulation is provided by dead air spaces within the material

Question 29

Countercurrent circulation in extremities

Answer 29

In a cold environment, that loss of heat would be a liability

Imagine a whale’s flipper. To fulfill its primary function—powerful swimming strokes—it must (1) stick out into the water, (2) have a large surface area, and (3) be thin

These mechanical constraints all make the flipper a terrible liability with respect to heat loss. However, this liability can be reduced by an arrangement of blood vessels called countercurrent circulation

This simply entails direct contact between the arteries that send warm blood out to the flipper and the veins that bring cooled blood back to the body
With these vessels closely appressed, heat exchange can occur between the arterial and the venous blood

This means that the cooled returning venous blood captures warmth from the outgoing arterial blood before that warmth can be lost to the environment
Instead, the returning venous blood carries that heat right back into the animal’s core

Furthermore, because the blood flows are going in opposite directions (countercurrent), there is a continuous temperature gradient between the two vessels (see schematic diagram in lecture slides)
Therefore, the transfer of heat continues along the entire appressed length of the paired vessels

Question 30

evaporative cooling

Answer 30

Because of water’s great heat of evaporation, exposing moist surfaces to air flow is a very effective way to cool a body

Sweating works best with bare skin, so it is particularly effective for humans
Mammals that are mostly covered with fur, such as familiar cats and dogs, sweat from exposed skin such as paw pads

They also achieve evaporative cooling through panting, which draws air over wet surfaces of the tongue, pharynx, and lungs

Birds achieve most of their evaporative cooling through their respiratory system, which includes a system of air sacs that provides a more continuous flow, rather than the less efficient in-and-out airflow of mammals

Question 31

Environments that would be dead zones for humans and many other animals are comfortable homes for species with appropriate …

Answer 31

adaptations

Question 32

physiological ecology

Answer 32

-physiologists study how organisms acquire energy and nutrients and tolerate physical conditions
-ecologists study how organisms deal with their environ and how the environ limits where they live
-physiological ecology or “ecophysiology” is simply the study of physiology in the context of an organism’s ecology

Question 33

ranges of tolerance limit..

Answer 33

distribution

Question 34

maintenance of homeostasis requires energy and is often limited by …

Answer 34

constraints and tradeoffs

-e.g. homeotherms have to eat more

Question 35

an organisms physiology reflects …

Answer 35

the climate and other conditions to which the organism is adapted

Question 36

why do temperate animals in high latitudes have more variation

Answer 36

bc of tolerance

Question 37

seasonal temp variation is ____ near the equator and ______ with latitude

Answer 37

low; increases

Question 38

poikilotherms and heat balance

Answer 38

cold blooded animals that eat less (dont need to stay warm)

-lack physiological means to deviate from environ temp, their temps fluctuate

Question 39

homeotherms and heat balance

Answer 39

mammals, birds

-must regulate heat balance to keep internal temp within a narrow range: many traits contribute

Question 40

why do poikilotherm have LOWER energy requirements than homeotherms

Answer 40

maintaining a constant internal temp requires energy (they eat less+ dont need to eat to stay warm)

Question 41

radiation

Answer 41

heat transfer by electromagnetic radiation

Question 42

conduction

Answer 42

transfer by direct contact with substrate (e.g. feet lose heat to ground)

Question 43

redistribution

Answer 43

circulatory system redistributes heat among body parts
-esp core to appendages

Question 44

size and heat

Answer 44

-size matters to heat balance
-homeostasis and surface area:volume ratio
-volume provides the inertia

Question 45

surface area determines…

Answer 45

equilibration rate

Question 46

radius:1, SA/V:3 (smallest)

Answer 46

equilibrates quickly
-shed heat quicker
-better for hot environ

Question 47

radius:3, SA/V:1 (biggest)

Answer 47

equilibrates most slowly
-shed heat slower
-retains heat
-better to

Question 48

bergmann’s rule

Answer 48

homeotherms tend to be larger at higher latitudes (colder)
-low sa –> retain heat better

Question 49

allen’s rule

Answer 49

homeotherms tend to have smaller appendages at higher, colder latitudes

e.g. big ears facilitate heat loss

Question 50

how does countercurrent circulation to limbs conserve heat

Answer 50

-arteries and veins should be appressed in appendages to conserve heat; separated in appendages designed to shed heat

-countercurrent flow maintains gradient, so heat is always flowing from outgoing blood to incoming blood

Question 51

example of a trade-off

Answer 51

skinny weasel in cold climates
-being long and thin makes weasels subject to thermal stresses (costly)
-but allows them to be better predators (beneficial)
-bc they are long and thin, we infer that the fitness gains of being a good hunter offset the fitness costs of an expensive metabolism
-if they can’t get enough prey, they can stay warm despite their heat-wasting shape

benefits outweigh the cons

Question 52

2 reasons why natural selection produces deeply imperfect organisms

Answer 52

1) trade-offs
-being good at x may not necessarily imply being bad at y

2) constraints
-selection builds on whats already there, especially existing developmental programs
-more like tinkering