Natural Selection

Question 1

Unpredictability of Evolutionary Patterns

Answer 1

Evolution does not follow a predetermined or predictable pattern because it is influenced by random mutations, environmental changes, and genetic drift. These factors create diverse, non-linear outcomes rather than following a specific trajectory

Question 2

Gregor Mendel’s Contributions to Genetics

Answer 2

He discovered the basic principles of heredity through experiments with pea plants. He established the laws of segregation and independent assortment, demonstrating how traits are inherited through discrete units called genes

Question 3

Definition and Function of Genes

Answer 3

A segment of DNA that codes for a specific protein or function. Genes act as instructions for building and maintaining an organism, influencing physical traits, and controlling various biological processes

Question 4

Definition and Function of Proteins

Answer 4

Proteins are complex molecules composed of amino acids that perform a wide range of functions in living organisms. They can catalyze biochemical reactions, provide support, such as collagen in connective tissue, and carry molecules throughout the body. Their diverse roles are due to the vast variety of amino acid sequences and structures, allowing proteins to function in virtually every cellular process

Question 5

Definition and Significance of Mutations

Answer 5

Changes in the DNA sequence of an organism. They can introduce new genetic variations, which are the raw material for evolution, enabling populations to adapt to changing environments through natural selection. Mutations can be neutral, beneficial, or harmful, and their significance depends on the context of the organism’s environment

Question 6

Random and Non-Random Aspects of Mutations/Natural Selection

Answer 6

Mutations occur randomly and introduce new genetic variations, without regard to whether they are beneficial. Natural selection is a non-random process that favors beneficial mutations, increasing the frequency of advantageous traits in a population. Thus, while mutation is a random event, natural selection systematically shapes the direction of evolutionary change

Question 7

Theodosius Dobzhansky’s Quote

Answer 7

“Nothing in biology makes sense except in the light of evolution,” emphasizing that evolutionary theory is the foundation for understanding biological processes

Question 8

Impact of Population Bottlenecks on Genetic Variability

Answer 8

If all humans were destroyed by an epidemic except a single tribe in New Guinea, the global human gene pool would suffer a severe loss of genetic variability. This would lead to reduced diversity and increase the risk of genetic disorders in future generations

Question 9

Species

Answer 9

A group of organisms that can interbreed and produce fertile offspring. When living in the same geographical range, reproductive barriers, such as behavior isolation or incompatible mating rituals, keep species separate

Question 10

Importance of Genetic Variability

Answer 10

It is crucial for populations because it enhances their ability to adapt to environmental changes, resist diseases, and reduce the likelihood of extinction

Question 11

Ring Species

Answer 11

A group of geographically connected populations that can interbreed with neighboring populations but have diverged enough that the populations at the ends of the range cannot interbreed. This phenomenon illustrates gradual evolutionary change

Question 12

George Gaylord Simpson’s View of Directed Evolution

Answer 12

He argued that there is no evidence for directed evolution, meaning that evolutionary changes are not guided by a predetermined plan or purpose. Instead, they are shaped by natural selection acting on random mutations

Question 13

Overproduction in B Cell Evolution

Answer 13

B cells are produced in large numbers, similar to the overproduction of offspring in natural populations. This ensures a diverse array of B cells exists, increasing the likelihood that some will be able to recognize and respond to a wide range of pathogens

Question 14

Heritable Variation in Receptors in B Cells

Answer 14

Each B cell has unique receptors on its surface, which are genetically determined and passed through cell division. This diversity is akin to heritable variation in organisms, providing the immune system with the potential to recognize and bind to a broad array of pathogens

Question 15

Selection of Effective B Cells

Answer 15

Only B cells with receptors that can bind effectively to an antigen are selected to proliferate. This selection process mirrors natural selection in larger populations, where only individuals with beneficial traits survive and reproduce

Question 16

Clonal Selection in B Cells

Answer 16

When a B cell receptor weakly binds to an antigen, the immune system selects that B cell for clonal expansion. This process leads to the production of a large population of nearly identical B cells, enhancing the body’s ability to fight the pathogen

Question 17

Genetic Rearrangement and Hypermutation of B Cells

Answer 17

During clonal expansion, antibody genes undergo genetic rearrangement and hypermutation, creating slight variations in the receptors. B cells with better binding receptors are selected, while poorly binding ones are eliminated, similar to how advantageous mutations are favored in evolution

Question 18

Formation of Memory B Cells

Answer 18

After repeated rounds of selection and adaptation, a group of memory B cells is created. These cells have receptors that bind almost perfectly to the pathogen and are retained in the body for future encounters, enabling a faster and more effective response

Question 19

Primary vs Secondary Immune Response

Answer 19

The primary immune response occurs when the body is first exposed to a new pathogen, leading to a slow and weak antibody production. The secondary immune response is faster and more robust due to the presence of memory B cells, which allow the immune system to recognize and respond to the pathogen more efficiently

Question 20

Immunity Explained

Answer 20

Occurs when the body is equipped with memory B cells that can rapidly produce antibodies upon re-exposure to a pathogen, preventing illness. Vaccinations mimic this process by stimulating the primary response without causing disease

Question 21

Role of Vaccines in Immune Response

Answer 21

Vaccines simulate the primary immune response, preparing the immune system to launch a strong secondary response if exposed to the actual pathogen. This reduces the risk of severe illness and promotes long-term immunity

Question 22

Pathogen Evolution and Vaccine Updates

Answer 22

Pathogens like flu viruses evolve rapidly, altering their surface proteins and evading immune detection. As a result, vaccines must be updated regularly to match circulating strains, ensuring continued protection

Question 23

Adaptation Through Natural Selection in Immune Responses

Answer 23

The immune system’s adaptation to pathogens mimics natural selection. B cells with more effective receptors are selected and proliferate, leading to a stronger and more specialized immune defense

Question 24

Danger of Primary Response Without Vaccination

Answer 24

Without vaccination, the first exposure to a pathogen can be dangerous because the primary immune response is slow and weak. The delay in producing sufficient antibodies can lead to severe illness or death before the immune system fully adapts

Question 25

David Reznick’s Guppy Experience Overview and Purpose

Answer 25

Reznick studied guppy populations in Trinidad to understand how predation affects life history traits like growth rate, sexual maturity, and body size. His research used natural experiments to demonstrate rapid evolutionary changes in response to varying predation pressures

Question 26

Life History Variation in Guppies

Answer 26

Life history traits, such as growth rate and timing of sexual maturity, vary among guppies and are genetically controlled, making them subject to natural selection. These traits determine how individuals balance growth, reproduction, and survival

Question 27

High-Predation vs Low-Predation Environments in Guppies

Answer 27

In high-predation environments, guppies mature faster, reproduce earlier, and produce more offspring. In low-predation environments, guppies grow larger, mature later, and invest more resources into fewer offspring, resulting in healthier individuals

Question 28

Experimental Transplant of Guppies

Answer 28

Reznick transplanted guppies from high-predation areas to low-predation sites to test whether life history traits would adapt in response to the new environment. Over 11 years, these guppies evolved slower life histories, growing larger and maturing later, demonstrating natural selection in action

Question 29

Rapid Evolutionary Adaptations in Guppies

Answer 29

Reznick’s experiment showed that significant changes in life history traits can occur in just a few generations when selective pressures shift. This rapid response illustrates the flexibility and speed of evolutionary processes in natural selection

Question 30

Quantity vs Quality in Guppies

Answer 30

In high-predation environments, guppies prioritize producing many offspring quickly, but these offspring are smaller and less healthy. In low-predation environments, guppies invest more in each offspring’s health and survival, leading to fewer but more robust offspring

Question 31

Predictive Power of Natural Selection in Reznick’s Experiement

Answer 31

The experiment provided strong evidence for the theory of natural selection by showing how changes in predation pressure directly influenced the evolution of life history traits. The results demonstrate natural selection’s predictive power for understanding evolutionary dynamics

Question 32

Fitness and Relative Environmental Context in Guppies

Answer 32

The fitness of life history strategies is relative to environmental context. Rapid reproduction is favored in high-predation areas, while investing in offspring quality is advantageous in low-predation areas. There is no universally “optimal” strategy–success depends on specific environmental conditions

Question 33

Empirical Support for Natural Selection in Guppies

Answer 33

Reznick’s research provided strong empirical support for natural selection, showing how predation can drive evolutionary changes in a population’s life history traits within a relatively short timeframe

Question 34

Cichlids of Lake Victoria

Answer 34

They are fascinating due to their rapid speciation and incredible diversity, which provide insight to adaptive radiation and evolutionary processes

Question 35

Human Impact on Cichlids in Lake Victoria

Answer 35

Humans have detrimentally affected cichlids through introduction of the Nile perch, which preyed on native cichlids, pollution, leading to reduced water quality and habitat loss, and overfishing, depleting cichlid populations and disrupting the ecosystem