Evolution

Question 1

What is evolution?

Answer 1

Evolution is a change in the characteristics of living things over time, resulting in the development and diversification of species.

Question 2

What is natural selection?

Answer 2

Natural selection is the process by which some members of a species, being better adapted to their environment, produce more offspring than others, leading to the transmission of advantageous traits to their offspring over generations.

Question 3

Who is associated with the theory of evolution and when was the theory presented?

Answer 3

Charles Darwin is most associated with the theory of evolution, and he presented his theory in the book “On the Origin of Species” in 1859.

Question 4

Explain the concept of common ancestry in the theory of evolution.

Answer 4

Common ancestry suggests that different species share a common ancestor from which they have evolved. For example, humans and modern apes have a common ancestor that lived several million years ago.

Question 5

What is one common misconception about evolution?

Answer 5

One common misconception is that evolution explains the origin of life on Earth, whereas it actually explains how life changed and diversified after its initial appearance.

Question 6

How were the first organic molecules likely formed?

Answer 6

The first organic molecules were likely formed by simple carbon-based molecules combining with other simple molecules, possibly through chemical reactions caused by lightning in Earth’s early atmosphere.

Question 7

When did these first organic molecules likely form?

Answer 7

The first organic molecules likely formed as early as 4 billion years ago.

Question 8

What gases were present in Earth’s early atmosphere, according to the hypothesis?

Answer 8

Earth’s early atmosphere is thought to have contained gases such as ammonia, methane, water vapor, and carbon dioxide.

Question 9

Who conducted the Miller-Urey experiment, and what did it demonstrate?

Answer 9

Stanley Miller and Harold Urey conducted the Miller-Urey experiment, which demonstrated that organic molecules could form under simulated conditions of early Earth’s atmosphere. The experiment suggested that simple organic molecules could arise from inorganic chemicals through simulated lightning and the right atmospheric conditions.

Question 10

What is the RNA world hypothesis?

Answer 10

The RNA world hypothesis speculates that RNA (ribonucleic acid) may have been the first organic molecule to evolve and serve as the basis of early life on Earth. This hypothesis suggests that RNA could encode genetic information like DNA and perform chemical reactions similar to proteins, resolving the question of which of these molecules came first in evolution.

Question 11

How did the first eukaryotic cells likely evolve?

Answer 11

The first eukaryotic cells likely evolved through endosymbiosis, where large cells engulfed small cells. These small cells formed a symbiotic relationship with the larger cells, eventually evolving into organelles like mitochondria and chloroplasts.

Question 12

What were the small cells that entered into a symbiotic relationship with larger cells in endosymbiosis?

Answer 12

The small cells that entered into a symbiotic relationship with larger cells in endosymbiosis evolved into organelles. Some of them became mitochondria, which broke down the large cell’s wastes for energy, while others became chloroplasts, capable of using sunlight to make food.

Question 13

What evidence supports the endosymbiotic theory for the evolution of mitochondria and chloroplasts?

Answer 13

Organelle DNA is short and circular, distinct from nuclear DNA.
Membranes of these organelles resemble prokaryotic membranes.
Ribosomes within these organelles are similar to bacterial ribosomes.
Reproduction occurs through binary fission, not mitosis.
Biochemical pathways and structures show closer relationships to prokaryotes.
Two or more membranes surround these organelles.

Question 14

How does the evolution of eukaryotic cells explain the subsequent diversity of life on Earth?

Answer 14

The evolution of eukaryotic cells played a pivotal role in the diversity of life on Earth. These cells, made possible by endosymbiosis, had the potential to evolve characteristics like multicellularity, cell specialization, and large size. This laid the foundation for the wide variety of animals, plants, and fungi that exist today. Eukaryotic cells are the key to the diversity of life we see on Earth.

Question 15

How does the endosymbiotic theory connect eukaryotes to prokaryotic organisms?

Answer 15

The endosymbiotic theory suggests that mitochondria and chloroplasts within eukaryotic cells descended from prokaryotic organisms through endosymbiosis. The timing of this evolutionary event is not precisely determined, but it is estimated to have occurred about 2 billion years ago, allowing eukaryotic cells to emerge and eventually diversify into various forms of life.

Question 16

What is the study of similarities and differences in the structures of different species called?

Answer 16

The study of similarities and differences in the structures of different species is called comparative anatomy.

Question 17

What are homologous structures, and how do they provide evidence for evolution?

Answer 17

Homologous structures are structures that are similar in related organisms because they were inherited from a common ancestor. These structures may or may not have the same function in the descendants. Homologous structures provide evidence for evolution by indicating a shared ancestry, even if the functions of these structures have changed in different species.

Question 18

Give an example of analogous structures and explain why they appear similar in unrelated organisms.

Answer 18

An example of analogous structures is the wings of bats and birds. These structures look similar and serve the same function, but they evolved independently in the two groups of animals. They appear similar because they evolved to do the same job, not because they were inherited from a common ancestor.

Question 19

What is the study of the similarities and differences in the embryos of different species called, and how does it provide evidence for evolution?

Answer 19

The study of the similarities and differences in the embryos of different species is called comparative embryology. It provides evidence for evolution by revealing shared embryonic features among different organisms, even if some of these features are lost in adulthood. These shared features suggest a common ancestry.

Question 20

How can comparing DNA sequences contribute to the evidence of evolution, and what are the strongest pieces of evidence it provides?

Answer 20

Comparing DNA sequences contributes to the evidence of evolution by showing the degree of similarity in DNA among different species. The more similar the DNA sequences, the stronger the evidence for a closer evolutionary relationship and shared common ancestry. DNA comparisons provide some of the strongest evidence for evolution from a common ancestor.

Question 21

What was the scientific question that Alfred Wegener asked?

Answer 21

The scientific question that Alfred Wegener asked was whether the continents were once joined and then drifted apart.

Question 22

What evidence did Alfred Wegener have to support his idea of continental drift?

Answer 22

The fit of the continents, which appeared to fit together like puzzle pieces.
The distribution of ancient fossils of the same type of plants and animals on widely separated continents.
The presence of rocks of the same type and age on both sides of the Atlantic Ocean.
The matching mountain ranges across the Atlantic Ocean.
Evidence from ancient glaciers that was closer to the equator than expected.
Indicators of ancient climate found in locations where those climates do not exist today.

Question 23

Describe how Alfred Wegener used each type of evidence to support his idea of continental drift.

Answer 23

Wegener used the fit of the continents to show that they appeared to fit together, suggesting they were once joined.
He used the distribution of ancient fossils to indicate that organisms must have lived side by side when the lands were joined.
The presence of rocks of the same type and age on both sides of the Atlantic Ocean suggested that they formed side by side and later drifted apart.
Matching mountain ranges across the Atlantic Ocean indicated they formed as a single range before the continents split.
Evidence from ancient glaciers closer to the equator supported the idea that the continents had moved.
Indicators of ancient climate in areas where those climates do not exist today were explained by the movement of continents.

Question 24

Is fossil evidence considered evidence of evolution?

Answer 24

Yes, fossil evidence is considered strong evidence of evolution.

Question 25

What is a fossil?

Answer 25

A fossil is the preserved remains or traces of an organism from a past geological age, typically found in sedimentary rock.

Question 26

How do paleontologists learn about evolution?

Answer 26

Paleontologists learn about evolution by studying fossils, which provide a window into the past and demonstrate the evolutionary history of various species.

Question 27

Describe what fossils reveal about the evolution of the horse.

Answer 27

Fossils of horses reveal the evolution of the horse from small, four-toed ancestors that lived in wooded marshlands to modern horses with a single large toe (hoof), increased height for spotting predators in grasslands, and longer molars for grinding tough grasses and seeds. Fossil evidence illustrates the transformation of horse leg bones and teeth over 57 million years.

Question 28

What are the four forces of evolution?

Answer 28

The four forces of evolution are mutation, gene flow, genetic drift, and natural selection.

Question 29

Why is mutation considered a force of evolution?

Answer 29

Mutation creates new genetic variation in a gene pool, providing the genetic diversity necessary for other forces of evolution to act.

Question 30

What is the founder effect, and can you provide an example?

Answer 30

The founder effect occurs when a few individuals start a new population, and, by chance, the allele frequencies of the founders may be different from those of the population they left. An example is the small number of founders who established the Amish population in the U.S. and Canada, leading to unique genetic traits within this population.

Question 31

Why is genetic drift more likely to occur in small populations?

Answer 31

Genetic drift is more likely to occur in small populations because when a small number of parents produce just a few offspring, allele frequencies in the offspring may differ, by chance, from allele frequencies in the parents. In larger populations, these chance fluctuations tend to be averaged out, making genetic drift less significant.

Question 32

What is natural selection and what are its effects on allele frequencies?

Answer 32

Natural selection is the process by which individuals with traits that make them better adapted to their environment tend to survive and reproduce more frequently, passing those advantageous traits to the next generation. This leads to changes in allele frequencies within a population, favoring alleles associated with higher fitness.

Question 33

Describe three types of natural selection for a polygenic trait.

Answer 33

Stabilizing selection: This occurs when phenotypes at both extremes of the distribution are selected against, narrowing the range of variation.
Directional selection: In this case, one of the extreme phenotypes is favored, shifting the distribution toward that extreme.
Disruptive selection: Here, phenotypes in the middle of the range are selected against, leading to two overlapping phenotypes at each end of the distribution.

Question 34

How does the recessive sickle-cell allele stay in the gene pool?

Answer 34

The recessive sickle-cell allele (S) remains in the gene pool due to the advantage it confers in regions where malaria is prevalent. Heterozygotes (AS) with the sickle-cell allele are resistant to malaria and, therefore, have a higher fitness because they are more likely to survive and reproduce. This positive effect on fitness keeps the S allele in the gene pool.