Mechanisms of Evolution
What is natural selection?
This process impacts populations over many generations by favouring traits that help organisms survive and reproduce.
What are adaptations, and give three examples of adaptations?
An adaptation is a trait that helps an organism survive and reproduce in its environment. Structural = mimicry for butterflies; physiological = monarch butterflies taste bad to predators; behavioural =migration
Cuvier studied the fossils in rock strata at various locations. What trend did he find?
The fossils from deeper strata were the most unlike the fossils of upper strata.
What is the fossil record?
The remains and traces of past life that are found in sedimentary rock revealing the history of life on Earth and the kinds of organisms that were alive in the past
Define gene flow and give an example.
The net movement of alleles from one population to another due to the migration of individuals. E.g individuals in grey wolf populations travel long distances and may join or otherwise interact with members of other populations to increase gene flow
What is fitness?
Fitness is often described as the number of reproductively viable offspring that an organism produces in the next generation. An organism with many viable offspring has high fitness.
Explain how the two scenarios of the peppered moth is an example of natural selection.
The flecked peppered moth was adapted to the lichen coloured trees (had a selective advantage due to genetic variation). The black peppered both was adapted to the black coloured trees allowing them to survive, reproduce, and pass on favourable traitis to offspring.
Name the other naturalist who independently developed a theory of natural selection similar to Darwin's.
Alfred Wallace
Define a vestigial structure. Provide an example.
A structure that is a reduced version of a structure that was functional in the organism’s ancestors. E.g. pelvic bone in whales, ostrich wings, human appendix
Predict what might happen to the diversity of a gene pool if individuals with rare alleles migrate from the population.
If individuals with rare alleles migrate away from the population, the genetic diversity of the remaining gene pool will decrease. Loss of genetic variation occurs and populations become more genetically similar.
This type of selection is driven by humans and can lead to negative impacts. Provide an example of a negative impact.
Artificial selection.
Dog breeding. Pugs have respiratory issues because of their squashed faces.
How does natural selection influence adaptations?
Natural selection drives adaptation that favours traits that improve survival and reproduction. Many generations later, beneficial traits become more common in a population. Over time, organisms are better suited to their environment through behavioural, structural, and physiological adaptations.
How might Lamarck have explained an elephant’s long trunk?
Lamarck would explain that an elephant’s long trunk was formed by the previous generation of elephants repeatedly stretching their short trunks to reach food and water, and that this acquired trait was then inherited by their offspring over generations (inheritance of acquired characteristics). Disuse of the trunk for food and water would result in the gradual loss of this trait of the long trunk (use and disuse).
What are transitional fossils? Give an example and explain how it is a transitional fossil?
Fossils that show a link between two groups, as evidence of change of species over time. E.g., Archaeopteryx- bird-like (feathers) and reptile-like fossil (teeth, bony tail, etc).
Explain why microevolution applies to populations but not to individual organisms.
Microevolution is a change in the overall mix of genes across a whole group over time (an individual's genes are permanent from birth to death and DNA doesn't change over one lifetime). When individuals with helpful traits survive and reproduce, those specific genes become more common in the next generation.
What is selective pressure? Give an example.
election pressure refers to any factor that affects the survival and reproductive success of individuals within a population. Factors such as light intensity on young trees act as forces, influencing which organisms survive in a given environment.
A black and yellow insect starts buzzing around your head. You swat it away, trying to avoid it because it looks like a stinging insect. It lands on your arm, and you see that it is a harmless fly. Explain the fly’s adaptation (be specific) and what the advantage is to the fly.
Mimicry - a structural adaptation - mimicking a bee or wasp to avoid predation or to increase the ability to survive in nature.
List the four key points Charles Darwin theorized.
1. Organisms produce more offspring than can survive.
2. Therefore, organisms compete for limited resources.
3. Individuals of a population vary extensively, and much of this variation is heritable.
4. Individuals that are better suited to local conditions survive to produce more offspring. Processes for change are slow and gradual.
State two contrasts between homologous and analogous structures and give examples.
Contrast 1 - analogous structures show similar functions but different structures, (e.g. wings of birds and butterflies have function of flying but different anatomical structures) whereas homologous structures show similar structures but different functions e.g. horse, porpoise, human pentadactyl limbs.
Contrast 2 - analogous structures show NO COMMON EVOLUTIONARY HISTORY, whereas homologous strucures do.
An imaginary population of mouse-like “meeps” lives in tunnels under a vegetable garden, which is the source of their food. About 80 percent of the meeps have green fur, and the rest have grey fur. One summer, a dust storm covers the garden with a coating of grey-brown soil. Th e people who tend the garden can now easily see the green meeps and are better able to trap and remove them humanely to protect their crops. Predict at least one outcome of this situation on the microevolution of this population of meeps as time passes. (Assume that similar dust storms happen every few years.)
Grey furred meeps will increase over time, while the green fur trait will decrease.
The grey-brown soil camouflages the grey meeps, so they are more likely to evade the gardeners, survive, and reproduce. The green meeps, being highly visible, are removed from the breeding pool before they can pass on their genes. As these dust storms recur the grey fur will dominate the gene pool.
Explain how antibiotic resistance develops and draw a diagram to support your answer.
A random genetic mutation can give bacteria a new allele, leading to resistance to certain antibiotics, allowing the bacteria to survive, reproduce, and pass on the trait to offspring.
In a population of sparrows, most birds have a beak that is about 10 mm long. Some birds, however, have beaks that are slightly longer or slightly shorter than the average. Explain why this variation within the population is important in terms of survival of individual sparrows.
Some beak shapes are better suited to environments that may be changing. Variation in beak shapes or sizes helps sparrows survive in changing conditions to access a wide variety of food sources. This also reduces competition between birds.
Explain why Darwin used the phrase descent with modification rather than evolution.
Darwin felt the word evolution implied progress, that each generation was somehow improving in some way. Natural selection does not demonstrate progress; it has no set direction, but rather is based on how adaptations possessed by individuals are passed on (traits for survival already possessed).
What is embryology and state three ways it shows evidence of evolution?
The study of early, pre-birth stages or an organism's development. It shows a common ancestry because of the similarities between verterbrate embryos:
1. paired pouches in the throat
2. Development of tails
3. Gill slits
State one comparison and one contrast between
PREZYGOTIC MECHANISMS
POSTZYGOTIC MECHANISMS
Comparison - both are mechanisms for ensuring that the same species mate.
Contrast - prezygotic occurs before fertilization. Postzygotic occurs after fertilization (to ensure the same species are mating and producing fertile offspring).