Ecology
What is the difference between laboratory and field experiments? Be specific.
Laboratory experiments - allow exact regulation of factors such as light, temperature, moisture, interactions
Field experiments - conducted outdoors; operating on natural rather than artificial populations
What is it called when competition adversely affects a species and the total biomass is lower in a mixture than monoculture?
underyielding
What is fitness?
An organism's ability to survive and reproduce
What feature is different between stickleback that live in the ocean, and some fish that live in freshwater lakes?
Spines! Stickleback living in the ocean have spines. Some freshwater species have evolved without spines.
What is a fossil?
Remains or traces of organisms from that past that are found in sedimentary rock
What is the difference between inter and intraspecific competition?
Interspecific competition is between individuals of DIFFERENT species. Intraspecific competition is between individuals of the SAME species.
Define destructive sampling.
When an organism must be permanently changed or destroyed in order to collect data
Define natural selection
A process in which individuals that have certain inherited traits will survive AND reproduce at higher rates than other individuals because of those traits
What environmental variable is driving natural selection (and evolution) in stickleback fish?
presence or absence of predators
What is the law of succession?
Fossils and living organisms in the SAME region resemble each other
Define exploitation competition.
Organisms compete through consumption of a limited resource (like light, water nutrients, nesting habitat), without physical interference
What is a null hypothesis and when would we refute it? Give an example.
A null hypothesis is the opposite of the hypothesis and generally states there is no difference. It is refuted when p < 0.05.
Examples vary – The average height and weight of oats is the same in 50:50 mixtures and in monoculture.
State two types of evidence for microevolution and a specific example of each.
Artificial selection (wild mustard, dogs, etc.)
Direct observation in natural populations (drug resistance in bacteria)
Vestigial structures (kiwi wing nubs, pelvic girdles in snakes)
Give an example of sampling bias in the collection of stickleback fish.
Examples may vary:
- researchers collected fish only in shallow water because it was easier to place traps there; as a result, they might miss individuals living in deeper water, which could have different traits
- By using traps to catch fish, researchers might catch only the most daring and inquisitive individuals in a population; this might result in a sampling bias if researchers are studying traits associated with behavior
Explain how molecular homology provides evidence for common ancestry.
Mutations or flaws in the DNA, included repeated gene sequences, are present in closely related species and show common ancestry. The genetic code is also universal!
Describe TWO possible reasons for species to co-exist in nature.
Predators or disease keeping populations small, resource partitioning, morphological differences, patchy environment, disturbance regimes
What is the t-statistic and what information is needed to calculate it?
The t-statistic is the likelihood of finding a particular difference between two averages when the null hypothesis is true. In other words, it is the likelihood two averages will be different by chance alone. The mean, standard deviation, and sample size (n) are needed to calculate it.
Explain the difference between convergent evolution and anatomical homologs. Provide an example of each.
Convergent evolution is the independent evolution of similar features in distantly related groups. Features have the SAME function, but DIFFERENT ancestry. Examples: Sugar glider and flying squirrel, or shark and whale.
Anatomical homologs have the DIFFERENT functions, but the SAME ancestor. Example: forelimbs in mammals.
Why are random samples, rather than entire populations, used in research studies?
It would take too much time and money to study all individuals in a population. As a result, scientists study randomly collected subsets of individuals from a population, or random samples. Scientists study random samples to estimate properties of the population and infer conclusions about the population as a whole.
Explain the process of creating digital specimens, and explain how this new technology is improving evolutionary research.
Images are scanned with micro-CT machines and reassembled using computer programs. They are anatomically accurate and precise. These are then uploaded to databases where scientists all over the world can access them. This allows more fossils and specimens to be viewed and analyzed all over the world without transporting the delicate specimens, which has led to incredible advancements in evolutionary science.
Describe the de Wit replacement series. What does it compare?
Experimental design to examine competing species.
Used to compare intraspecific vs. interspecific competition by pairing monocultures and mixed cultures.
Given the following information, does corn experience intraspecific competition, interspecific competition, both, or no competition?
Mean height grown in 25 monoculture: 52
Mean height grown in 50 monoculture: 48
Mean height grown with beans: 62
P-values for 25 vs 50 (0.04), 25 vs mixed (0.03), or 50 vs mixed (0.02).
Corn experiences intraspecific competition. It does not experience interspecific competition - in fact, there is a facilitative effect with beans.
Describe the four ways that genetic variants can be produced and how does this contribute to evolution.
Formation of new alleles (mutations), Altering gene number or position, Rapid reproduction, Sexual reproduction
More variation in a population provides more traits to be selected by natural selection in a given environment. New variants may do better in an environment and will survive and reproduce at a greater rate, leading to potentially new species, or divergence in lineages.
In the Stickleback lab, you sampled Bear Paw, Frog, and Morvoro lakes. You found that fish in Bear Paw Lake had NO spines, fish in Frog Lake ALL had spines, and Morvoro Lake had some fish with spines and some without. You investigate further and find that Bear Paw and Morvoro have no predators present, while Frog Lake has predators. Why do fish in Morvoro Lake still have spines? What is the best explanation for this?
There are two possible explanations:
It is possible that the population in Lake Morvoro is in the process of changing from a population of fish with mainly pelvic spines to one without pelvic spines.
OR there was a predatory fish in the lake when the stickleback population first colonized the lake, but that predator is no longer there (e.g., all the trout were caught).
One important evolutionary change is the transition of aquatic mammals (i.e., whales and dolphins) from land to water. This transition is well documented by a series of intermediate fossils. Some defining anatomical features of this transition are the loss of hindlimbs. Place Species A – D in order from oldest ancestor (land mammal) to the modern whale skeleton (Species A). Explain your answer. (See Quiz 2 Review handout for images)
Correct order is B, D, C, A. B has well-developed hindlimbs and pelvic structure. Leg length then begins to shorten as species spend more time in aquatic environments