Midterm 2 Prep Flashcards
Features exhibited by mammal-like reptiles that identify them as relatives of modern mammals
- Lower jaw composed of a single bone (mammals), rather than several (reptiles).
- Teeth differentiated into various types (mammals) (eg. Incisors, canines, molars, etc.) vs one type (reptiles).
- Inner ear has several bones which mechanically transfer sound to the auditory apparatus (mammals) rather than one or none (reptiles).
What is a trophic cascade? Draw as an example, one of the trophic cascades described in the paper and identify the consequences of that cascade on the organisms in the system.
A trophic cascade is a top-down process where higher trophic levels suppress organisms in the next level down (e.g., predators suppress herbivores), which can reduce pressure on the level below that (e.g., suppression of herbivores allows plants to increase in density).
In areas without Orcas, otters suppress urchins and kelp increases…
What is the main reason that plants require copious quantities of water in order to conduct photosynthesis?
CO2 can only be taken up across a wet membrane, which means that water must be lost by evaporation in order for CO2 to be absorbed.
Taphonomic bias
Overrepresentation of easily-fossilized species in the geologic record or the underrepresentation of species that do not easily fossilize. Thus animals with mineral shells such as many molluscs fossilize very well and animals without any hard parts such as nematodes or earthworms rarely fossilize. It is important to keep this in mind because taphonomic bias gives us an inaccurate picture of the organisms present in the past.
What is an Allee effect? What mechanism (explain one) can produce an Allee effect?
An Allee effect is the phenomenon where a population exhibits reduced or negative growth rates (i.e, starts to decline) when it is at a very low density. There are a number of mechanisms that can produce this effect.
- inability/too much time required to find a mate to the point where rate of reproduction is reduced.
- (in plants) insufficient transfer of pollen reduces seed production below the levels plants could potentially make.
- breakdown of social facilitation systems which compromise hunting success, help in offspring care and feeding, ability to detect predators quickly, etc.
What does low water potential in soil signify? Explain one negative consequence of low soil water potentials for plants.
Low water potential in soil indicates dry soil where the water present is tightly bound to the soil particles. Plants need to generate even lower water potentials in their leaves in order to take it up and that is difficult to do. Water is thus in very limited supply and since water is needed for CO2 uptake, low soil water potentials limit plant growth and reproduction.
When someone compares two phylogenetic trees and makes the statement that one is more parsimonious than the other, what do they mean?
A maximally parsimonious tree is one that requires the fewest evolutionary changes among all of the possibe trees that can be constructed to classify a group of organisms.
What exactly is a numerical response? Identify and explain the two mechanisms that can produce a numerical response.
A numerical response is the change (increase) in the numbers of predators as a function of a change (increase) in the numbers of prey. This can happen via one or both of the following mechanisms.
- an aggregative response: movement of predators to areas of high prey density
- a demographic response: increased rate of reproduction by predators when prey are numerous which results in increased predator density.
Overriding abiotic factors that affect the distribution of terrestrial/aquatic organisms
Sunlight, distribution, water, O2
Reasons why we seldom see actively occurring competition in nature
Changes in environment, encounters of predators has already occurred
Parameters that can be used to describe a community
Abundance, richness, community composition, dominance, and evenness
Outgroup
a species that will not be part of our tree that we can assume retains some of the ancestral characters
- relatives to the ingroup but less closely related to them than the members of the ingroup
How molecular data can be used in creating phylogenies
Compare regions of the genome that are not under natural selection (ie. non coding DNA, beta-casein gene) in different organisms
- useful if morphological evidence is not available
- can use each site in the sequence as a separate character to look for synapomorphies
- then generate all possible classifications with a computer
Ways we can get fossils
- minimal change (amber and freezing)
- permineralization and replacement (happens over long timescales, tissue replaced by silica)
- molds and casts (dead organism preserved in sediment, when organism rots away a mold is left)
- trace fossils (stuff left behind by an organism that isnt necessarily part of the organism itself)
Example of a major change in the Earths biota that happened as a result of the mass extinction (Permian - Triassic)
- massive loss of marine invertebrates
- massive loss of insects
- loss in diversity overall
Fundamental niche
Range of environmental conditions within which that species can maintain a population that reproduces frequently enough that the population doesn’t shrink
