Ecology Exam

Scattered notes:

Endotherms can generate their own heat

Ectotherms need to find heat sources

Brown fat can act as a heat source.

During entry into hibernation. blood pressure and oxygen consumption decrease

Quiz Questions:

Question 1: How do we calculate the threshold value? Contains graph with equation. How many day degrees (after 10 days)?

The equation is given: 0.0124x-0.1384=y

The threshold value is when the developmental rate is at 0. (y=developmental rate)

Thus: 0.0124x - 0.1384 = 0 add 0.13 and then divide by 0.0124

x = 11.16

Calculate day degrees by taking 0.1 and making it the developmental rate:

0.0124x-0.1384=0.1 then x = 19.23

Then subtract the threshold value from this one = 19.23 - 11.16 = 8.07

day degrees over course of 10 days = 10 x 8.07 = 80.7

Question 2:

What principle causes the downward trend? The temperature size rule: warmer temps = faster growth, but smaller size

Dry mass refers to the size.

Development usually increases faster with temperature than growth. Therefore, the final size decreases with rearing temperatures.

Question 3: Give 3 examples of endothermic organisms, each from a different phylum. (note: chordates are 1 phylum!)

  • All birds and mammals, bluefin tuna, porbeagle sharks, swordfish, sea turtles (phylum Chordata)

  • Bumblebees, termites, honey bees, some butterflies, some moths, some dragonflies (phylum Arthropoda)

  • Some squid and octopus (phylum Mollusca)

Question 4: Both endotherms and ectotherms pay a price for living at suboptimal temperatures.

a. What price does the endotherm pay?

The endotherm pays the price of using energy to conserve heat instead of energy for other functions such as hunting.

b. What price does the ectotherm pay?

Sub-optimal performance over a large temperature range (lower reproduction rates, slower growth)

Question 5: What are the benefits and costs of the freeze-avoiding strategy?

Benefits: the organism can withstand temperatures below freezing point

Costs: Production of anti-freeze components is energy-demanding

Question 6: Give 5 examples of organisms that use temperature as a stimulus for a biological response and give the type of response

  • Trees (growth or shedding of leaves in response to increasing temp)

  • Hibernating animals like snakes, bears or bats (start hibernating in response to daylength and temperature)

  • Many plants produce seeds that start to come out of a dormant state in response to temperature

  • Many mammals like horses, foxes, and cattle (start to grow or loose winter fur in response to temperature)

Question 7: Temperatures measured for constructing isotherms on maps are rarely the same as temperatures experienced by the organisms. Explain why.

These isotherms are based on the average temperatures in an area, but there are huge temperature variations between microenvironments. Even within an area, temperature changes drastically.

Question 8: The picture shows that the distribution of wild madder (Rubia peregrina) is closely related to the January 4.5ºC isotherm.

It is tempting to assume that this organisms distribution is regulated by temperature. However a correlation doesn´t necessarily mean that temperature is the causal factor!

  1. Give a possible alternative explanation of the observed correlation.

  • Competition with another plant species that is sensitive to the temperature, the wild madder is outcompeted north of the isotherm but the competitor does not grow south of it.

  • Predation by an insect that is sensitive to temperature and only lives north of the isotherm

  • Wild madder has a specific pollinator that is sensitive to temperature and only lives south of the isotherm

  • Wild madder has an association with a mycorrhizal fungus that is sensitive to temperature and only lives south of the isotherm

b. How could you test whether or not the winter temperature is the factor causing the distribution of this plant?

Grow wild madder in the laboratory to see what the temperature range is in the absence of competitors and predators.

Question 9: What are the options for surviving a very cold winter? (name 3)

  1. To remain active

  2. To migrate to another habitat for the duration of an inhospitable cold season

  3. To endure the periods of low-temperature extremes in the chosen habitat at low metabolic cost by reducing T b, locomotion, and other life functions at all levels

Question 10: What is the difference between torpor and hibernation?

  • Torpor : entry of the whole animal into a state of hypothermia which is accompanied by behavioral inactivity, regulated by a combination of external and internal signals.

  • Hibernation: a sustained and profound state of torpor

Question 11: What characteristics would you expect to find in seasonal hibernators? (name 3)

  1. small body size

  2. Live in an environment where there may be a large difference between T a and T b

  3. Their food is likely to be absent or inaccessible for long periods

Question 12: In what way do the data in the table below suggest that Tb is controlled in the hibernating marmot?

The T b in each experiment remained relatively constant, varying only between 4.1° C and 4.7° C, but the heat production varies, being very much higher when T a was held at the lowest temperature.

Question 13: What are the 3 most important environmental stimuli (or exogenous cues) initiating torpor?

  • food supply

  • daylength

  • T a

Question 14: What are facultative and obligate hibernators?

  • Facultative hibernators hibernate in response to environmental conditions

  • Obligate hibernators have a cycle of hibernating and arousing that seems to be strongly driven by an endogenous annual cycle under physiological control.