SimUText Flashcards
state the difference between ecologists and evolutionary biologists
- ecologists study processes that relate to how organisms interact with each other and their environment
- evolutionary biologists study the processes that lead to change in the genetic composition of populations over generations
give examples of processes that ecologists study
population growth, nutrient cycling, competition, herbivory, and predation
examples of processes that evolutionary biologists study
speciation, extinction, adaptation
describe Pink bollworms and the issues associated with them
- adults are not problematic
- larvae (caterpillars) are pests of cotton: eat the flowers and seeds of cotton plants, reducing their fibre production and staining fibres
what makes the pink bollworm such a serious pest?
its capacity for explosive population growth. a single female can lay between 100 and 200 eggs.
a pink bollworm population can go through as many as —- generations during a single growing season
five
drawbacks of chemical insecticides
- toxic to humans and other animals
- expensive
- kill beneficial arthropods, including bollworm predators
- resistance can form
describe Bollgard
- cotton variety genetically engineered to produce its own biological insecticide
- gene from bacterium Bacillus thuringiensis (Bt) inserted into cotton plant’s genome
- encodes protein called Bt toxin Cry1Ac
- poisonous to the larvae of butterflies and moths
how does Bt toxin Cry1Ac harm caterpillars?
- when swallowed by a caterpillar, the toxin binds to molecules of cadherin (protein) in the membranes of the caterpillar’s midgut cells
- triggers series of events that disrupt the caterpillar’s digestion and kill it
what is the risk with usage of Bollgard?
there is a risk that species of moths may evolve resistance to Bt toxins
how are evolution and ecology intertwined?
evolution is often facilitated by ecological processes, and the resulting impacts can often be ecologically important
what are the four mechanisms of evolution?
mutation, natural selection, migration, and genetic drift.
are the four mechanisms of evolution exclusive of each other?
The four mechanisms of evolution (natural selection, genetic drift, migration, and mutation) do not act exclusively of each other. In natural populations, evolution can occur via any combination of mechanisms acting simultaneously.
when does evolution by natural selection happen?
when individuals with certain traits survive and reproduce at higher rates than others
the theory of evolution by natural selection consists of a set of 3 requirements for populations of organisms:
- there is variation among individuals
- at least some of this variation is passed genetically from parents to offspring
- some variants survive and reproduce at higher rates than others
what is the automatic consequence of all requirements for evolution by natural selection being met?
the composition of the population changes from one generation to the next. Traits associated with survival and reproduction become common; traits associated with early death and reproductive failure become rare.
when do alleles automatically change?
When there are differences in phenotype that are at least partly due to differences in genotype and some phenotypes have higher fitness than others. Alleles associated with high fitness become common; alleles associated with low fitness disappear. This is evolution by natural selection.
evolution by genetic drift.
Allele frequencies may also change across generations due to purely random events that result in sampling error
define the founder effect
a form of genetic drift that occurs when a few individuals from a source population establish a new population. Usually, the allele frequencies will be different in the new population than they are in the source population.
when does migration lead to evolution?
if it alters allele frequencies in one or the other populations
how does understanding the mechanism of descent with modification help researchers and farmers?
it helps them devise ways to control crop pests like the pink bollworm without encouraging rapid evolution of resistance
why do pink bollworm populations evolve resistance to Bt toxins?
because normally rare resistant genotypes enjoy much higher fitness than susceptible genotypes on Bollard cotton
how is the high-dose/refuge strategy effective in limiting the generation of resistance?
uses fields planted with patches of Bollgard and patches of normal cotton. The Bollgard cotton is well-protected against bollworms. The normal cotton allows susceptible bollworms to survive, reducing the fitness advantage associated with resistance.
describe fish present in Lake Washington
home to a population of threespine sticklebacks. These small fish are prey to cutthroat trout.
how do sticklebacks protect themselves against cutthroat trout?
- have bony plates in their skin that serve as armor.
- some sticklebacks wear a complete set of armor plating, some wear a partial set, and some wear a minimal set.
what is the benefit/cost of more armour plating?
- gives better protection against cutthroat trout, but this protection comes at a cost compared to lightly armored sticklebacks, completely armored individuals grow more slowly, survive
the winter at lower rates, and breed later. - in addition, because heavily armored sticklebacks grow more slowly, they are more vulnerable to predatory insects that eat juvenile fish.
where do sticklebacks tend to be more heavily armored
in lakes and streams where they are more vulnerable to attack by predatory fish, and less heavily armored where they are less vulnerable.
