Biology 100 Midterm 2 (part 2) Flashcards
Explain why humans continue to get sick despite natural immune systems and modern medicine.
Humans still get sick despite having natural immune systems and modern medicine because pathogens like bacteria and viruses constantly evolve to evade our defenses, new pathogens can emerge, people’s immune systems vary in strength due to genetics and lifestyle factors, and sometimes the environment facilitates the spread of disease, even with medical advancements; essentially, the arms race between humans and pathogens is ongoing, with pathogens often adapting faster than our immune systems can respond.
Define evolution, specifically evolution by means of natural selection.
Evolution, specifically through natural selection, refers to the process where a population of organisms undergoes changes in their heritable traits over generations, with those individuals possessing traits that better suit their environment being more likely to survive and reproduce, thus passing on those advantageous traits to their offspring, leading to a gradual shift in the characteristics of the population over time
Illustrate why antibiotic resistance is more common today than it was in the past
Antibiotic resistance is more common today than in the past because of the overuse and misuse of antibiotics.
Identify the smallest biological unit that can evolve.
Explanation: Evolution occurs through changes in the gene pool of a population over time, meaning that an individual organism alone cannot evolve, but a group of individuals within a population can experience evolutionary changes through natural selection
Describe Descent with Modification and explain what it means in modern scientific language.
“Descent with modification” refers to the core concept of evolution, meaning that species change over time through generations, with new traits being passed down from ancestors, leading to the emergence of new species that share a common ancestry; essentially, organisms gradually change and diversify as they reproduce, resulting in the diversity of life we see today.
Define microevolution.
evolutionary change within a species or small group of organisms, especially over a short period.
Define mutation and identify it as the source of variation within a population.
A “mutation” is a change in the DNA sequence of an organism, and it serves as the primary source of genetic variation within a population, as it creates new versions of genes (alleles) that can be passed on to offspring, leading to differences between individuals within a species
Identify and discuss different mechanisms of evolution (mutation, migration, genetic drift, natural selection)
The primary mechanisms of evolution are mutation, migration (also called gene flow), genetic drift, and natural selection; each contributing to changes in allele frequencies within a population by introducing new genetic variations, transferring genes between populations, randomly altering allele frequencies, or selecting for advantageous traits respectively.
Describe how the process of natural selection works, and how it results in adaptations.
Natural selection works by favoring individuals within a population that possess traits which give them a better chance of survival and reproduction in their environment, causing these advantageous traits to become more common in subsequent generations, resulting in adaptation to the environment over time; essentially, “nature selects” the best-suited organisms to pass on their genes, leading to a population better adapted to its surroundings.
Distinguish between founder effect and genetic bottleneck.
A founder event occurs when a small group of individuals is separated from the rest of the population, whereas a bottleneck effect occurs when most of the population is destroyed. The end result is very similar – genetic diversity is reduced.
Define a species
a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring.
Identify six reproductive barriers that can lead to new species.
Six reproductive barriers that can lead to new species are: behavioral isolation, temporal isolation, habitat isolation, mechanical isolation, gametic incompatibility, and hybrid inviability; these barriers prevent individuals from different populations from successfully mating, allowing for genetic divergence and the formation of new species over time.
Recognize the divergence of species through allopatric and sympatric speciation.
Allopatric speciation refers to the divergence of species when populations are geographically isolated from each other by a physical barrier, preventing gene flow and leading to separate evolutionary paths, while sympatric speciation occurs when new species evolve within the same geographic area without a physical barrier, usually driven by distinct ecological niches or genetic variations within the population.
Describe the theory of endosymbiosis that resulted in evolution of eukaryotic cells.
The endosymbiotic theory proposes that eukaryotic cells, which are complex cells with membrane-bound organelles, originated when a primitive host cell engulfed smaller prokaryotic cells (like bacteria) which then evolved into symbiotic organelles within the host, such as mitochondria and chloroplasts, essentially becoming a part of the larger cell through a process called endosymbiosis; this allowed the host cell to gain new functions like aerobic respiration (from mitochondria) and photosynthesis (from chloroplasts) that the prokaryotic ancestors possessed.
Identify evidence for the theory of endosymbiosis
The primary evidence supporting the endosymbiotic theory is that mitochondria and chloroplasts, organelles within eukaryotic cells, possess their own DNA which is circular like bacterial DNA, replicate independently through binary fission (similar to bacteria), have ribosomes resembling prokaryotic ribosomes, and have a membrane structure more similar to prokaryotic membranes than the rest of the eukaryotic cell; all indicating their origin from engulfed prokaryotic cells.
