17.Body Size Flashcards
Name some traits of a species that are affected by its body size.
Resource requirements, dispersal capacity, reproductive rate, evolutionary rate, interactions with other species
What is the different between interspecific and intraspecific?
Inter = between species
Intra = within species
What is Bergmann’s Rule?
Within related organisms, larger bodied species tend to be found in colder climates, and smaller bodied species in warmer climates
Is Bergmann’s rule inter- or intra- specific? What rule covers the other comparison?
Bergmann’s rule is interspecific, James’s rule often used for intraspecific examples
What types of species does Bergmann’s rule apply most accurately to?
Mammals and birds
What’s the difference between an endotherm and an ectotherm?
Endotherms - produce and store their own body heat
Ectotherms - rely on external heat
Does Bergmann’s rule apply best to endotherms or ectotherms?
Endotherms
Except for island environments, what is the best correlated factor with bird body size?
Temperature
What was Bergmann’s original reasoning for his rule?
Surface area to volume ratio
- Larger species have an advantage retaining heat in cold environments
How can dispersal abilities explain Bergmann’s rule?
Larger organisms have greater dispersal capabilities which could be an adaptive feature for low productivity, seasonal environments.
What suggested explanation for Bergmann’s rule involves competition?
Interspecific competition favours small body size and intraspecific competition favours large body size. Therefore small body size may be an advantage in high-diversity locations (tropics) and larger body size in less diverse regions.
Where are the widest ranges of plant heights found?
Cold, dry, low productivity environments
Where are shorter species of plants noticeably absent?
Wetter, warmer, more tropical environments
What would you expect Bergmann’s rule to show about body size in relation to elevation? Is this seen?
An increase in body size with elevation
- Results are ambiguous and inconclusive
What is deep sea gigantism? Is this due to temperature?
The tendency for species of deep-sea dwelling animals to display a larger size than their shallower-water relatives.
- Probably not
What is Foster’s rule also known as ?
The island rule.
What does Foster’s rule say?
In comparison with relatives on main-lands, small species tend to increase in size on islands and large species tend to decrease in size.
What is a likely explanation for larger animals following the island rule?
May adapt and become smaller because they are adapting to a resource poor environment.
What is a possible reason for smaller animals getting larger on islands?
Release from predation
What are island elephants a very good example of?
Foster’s rule
- Degree of dwarfism on the Asian islands is predictable from other islands, strong pattern of size
What is insular woodiness?
the evolutionary transition from herbaceousness toward woodiness on islands
What are some possible explanations for second insular woodiness?
Competition for sunlight may favour taller, stronger plants
Woodiness preserves water during droughts
Could be an indirect result of longer lifespan (lack of large native herbivores)
In the islands of what regions is IWS seen most?
Tropics and subtropics
Which set of islands represents about 19% of all transitions to IWS?
Canary Islands
How does distance to the nearest continent correlate with IWS rates?
Oceanic islands tend to have higher rates of IWS (further from continents)
How do IWS rates correlate with the amount of herbivore mammals?
Less herbivore mammals tends to mean more IWS
Is IWS more or less common on volcanic islands?
More
Describe a process by which volcanic eruption may increase IWS.
Shorter, more herbaceous plants are killed off by thick ash layers
- While taller, woodier plants are able to withstand or resprout
