Chapters 15 & 16 Flashcards
What is the total amount of genetic information in a population?
The gene pool
How do genetic variations arise?
Differences in genotypes arise by mutation, recombination, and the random pairing of gametes
How do you find phenotype frequency?
Phenotype frequency is equal to the number of individuals with a particular phenotype divided by the total number of individuals in the population
What frequency needs to be acted upon by an outside force in order to change?
Allele frequency
What is is a theoretical model of a population in which no evolution occurs and the gene pool of the population is stable?
Hardy-Weinberg genetic equilibrium
What is used to describe an non-evolving population?
Hardy-Weinberg genetic equilibrium
During Hardy-Weinberg Equilibrium, what has no effect on the overall gene pool?
Shuffling of alleles by meiosis and random fertilization have no effect on the overall gene pool
What are 5 assumptions of the H-W principle?
Large population size, no net mutations, no migration, random mating, no natural selection
What is the Hardy-Weinberg Equation?
1.0 = p squared + 2pq + q squared
Ø P squared = Frequency of AA genotype
Ø 2pq = frequency of Aa
Ø q squared = frequency of aa genotype
What can traits be mapped on? What does this map show?
Traits can be mapped on a bell curve, which shows that most individuals have average traits and very few have extreme traits
For Hardy-Weinberg Equilibrium to occur, what must happen?
The gene pool of a non-evolving population remains constant over multiple generations (allele frequency doesn’t change)
What can cause evolution to happen?
When populations are subject to genetic mutations, gene flow, genetic drift, nonrandom mating, or natural selection.
What is gene flow?
Gene flow- Emigration and immigration cause gene flow between populations and can thus affect gene frequencies
What is genetic drift and what kind of populations does it affect the most?
It’s the change in allele frequencies due to random events. It operates most strongly in small populations.
What can genetic bottleneck cause?
A drastic reduction in population due to volcanoes, earthquakes, landslides, etc; Reduced genetic variation; and the new smaller population may not be able to adapt to new selection pressures
What is the founder effect and what can it cause?
It occurs when a new colony is started by a few members of the original population. It causes reduced genetic variation and may lead to speciation.
What’s an example of genetic bottleneck?
Cheetahs- they have little genetic variation in the gene pool
This can probably be attributed to a population bottleneck they experienced around 10,000 years ago, barely avoiding extinction at the end of the last ice age.
Define nonrandom mating
Whenever individuals may choose partners
What occurs when a certain trait increases an individual’s success at mating?
Sexual selection
What can sexual selection help explain?
Sexual selection explains the development of traits that improve reproductive success but [may] harm the individual
What are the three types of natural selection?
Stabilizing, disruptive, and directional
What favors the formation of average traits?
Stabilizing selection
What favors extreme traits rather than average traits?
Disruptive selection
What favors the formation of 1 extreme trait?
Directional selection
What is a population of organisms that can successfully interbreed but cannot breed with other groups?
A species is a population of organisms that can successfully interbreed but cannot breed with other groups.
[According to the biological species concept]
What results from the separation of population subgroups by geographic barriers?
Geographic isolation
What results from the separation of population subgroups by barriers to successful breeding, such as different mating seasons?
Reproductive isolation
What is reproductive isolation within the same geographical area?
Sympatric speciation is reproductive isolation within the same geographical area
In what model do species undergo small changes at a constant rate?
In the gradual model of speciation (gradualism)
What is it called when new species arise abruptly, differ greatly from their ancestors, and then change little over long periods?
Punctuated equilibrium
What is the process by which modern organisms have descended from ancient organisms?
Evolution
-In 1831 who set sail from England aboard the HMS Beagle for a voyage around the world?
Charles Darwin
What did Darwin observe about the Galapagos during his time there?
Darwin observed that the Galápagos Islands were close together but had very different climates
What did Darwin begin to hypothesize on the voyage home?
Darwin wondered if animals living on different islands had once been members of the same species. If so, then he concluded that these separate species would have evolved from an original South American ancestor species
Why helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present?
Hutton and Lyell
Why did Lyell stress in /Lyell’s Principle of Geology/?
Lyell stressed that scientists must explain past events in terms of processes that they can actually observe [so people believe them]
What conclusions did Darwin come up with as a result of the understanding that the earth is millions of years old and has always had the same geological processes?
- If the Earth could change over time, life might change as well. 2. It would have taken many years for life to change in the way Lyell suggested 3. This would have been possible only if the Earth was extremely old.
Who recognized that:
Ø Living things have changed over time,
Ø All species were descended from other species,
Ø Organisms were adapted to their environments?
Jean-Baptiste Lamarck
Who proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime? What were the flaws in this theory?
Lamarck proposed that these traits could then supposedly be passed on their offspring. Over time, this process led to change in a species.
Other flaws include a tendency toward perfection and use and disuse
What didn’t Lamarck know?
How traits are inherited and that an organism’s behavior has no effect on its heritable characteristics
Who reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone?
Thomas Malthus
Who sent an essay [that basically summarized Darwin’s theories] for Darwin to review?
Alfred Wallace
Who did Darwin give his manuscript to to publish when he died?
His wife
What two things did Darwin say in his book?
He proposed a mechanism for evolution called natural selection and he presented evidence that evolution has been taking place for millions of years- and continues in all living things.
What is artificial selection?
When humans only breed organisms with desirable traits
How did Darwin come up with a scientific hypothesis to explain how evolution occurs?
Darwin compared processes in nature to artificial selection
What forces organisms to compete for resources?
High birth rates and a shortage of life’s basic needs forces organisms to compete for resources
The ability of an individual to survive and reproduce in its specific environment is its what?
Its fitness
Define fitness
The ability of an individual to survive and reproduce in its specific environment
What did Darwin propose about fitness and natural selection?
Darwin proposed that an organism’s fitness is a result of its adaptations, which is a result of natural selection
Why did Darwin refer to survival of the fittest as natural selection?
Because of its similarities to artificial selection
What is descent with modification?
The concept that natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. Also that each living species has descended, with changes, from other species over time
The idea that each living species has descended, with changes, from other species over time is called what?
Descent with modification
What are some things that give proof for Darwin’s theory that things have been evolving for millions of years?
The fossil record, geographical distribution, homologous structures, and similarities in early development, [or embryology]
What are similarities in early development of an organism?
Embryology
What shows that the types and distribution of organisms on Earth have changed over time?
The fossil record
What is the study of the locations of organisms around the world that provides evidence of descent with modification?
Biogeography
What is biogeography?
The study of the locations of organisms around the world that provides evidence of descent with modification
Do all homologous structures serve functions?
No
Structures that have different mature forms but develop from the same embryonic tissues are called what?
Homologous structures
Define homologous structures
Structures that have different mature forms but develop from the same embryonic tissues
The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. What are they called?
These organs are called vestigial organs
Define vestigial organs
The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species.
What develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates?
The same group of embryonic cells
What are some similarities in the development of many animals with backbones?
The early stages, or embryos, of many animals with backbones are very similar. The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates.
