Lecture 2

Question 1

What is evolution?

Answer 1

The change in the genetic composition of populations over time

This process involves changes in allele frequencies within a population.

Question 2

What contributes to differences among individuals within a species?

Answer 2

Genetic, or heritable, differences

These differences can affect physical traits, behaviors, and other characteristics.

Question 3

What does the process of natural selection predict about advantageous traits?

Answer 3

If a heritable trait confers an advantage, it will become more common over time

This process is a key mechanism of evolution.

Question 4

What happens to disadvantageous traits according to natural selection?

Answer 4

If a trait is disadvantageous, it will become less pervasive in the population over time

This leads to a gradual improvement in the overall fitness of the population.

Question 5

What are heritable traits encoded by?

Answer 5

Genes

Genes are functional linear stretches of deoxy-ribonucleic acid (DNA)

Question 6

Where is DNA contained within an organism’s cells?

Answer 6

Chromosomes within the nucleus

The nucleus is a membrane-bound organelle that houses the cell’s genetic material.

Question 7

How many genes does the human genome contain according to the Human Genome Project?

Answer 7

An estimated 20,000-25,000 genes

This estimate was provided in 2008.

Question 8

What results from the interaction of genes with the environment over time?

Answer 8

Evolution

Evolution is the change in the heritable characteristics of biological populations over successive generations.

Question 9

What is binary fission?

Answer 9

A method of reproduction where an organism splits in two

This method was used by the earliest known organisms with DNA.

Question 10

What type of organisms were the earliest known to use DNA as a genetic repository?

Answer 10

Microscopic, single-celled organisms

These organisms reproduced by binary fission.

Question 11

How do bacteria exchange DNA today?

Answer 11

Through a process called conjugation

This involves a hairlike tube called a pilus.

Question 12

What is a pilus?

Answer 12

A hairlike tube that connects bacteria for DNA exchange

It is used during the process of conjugation.

Question 13

What is a plasmid?

Answer 13

A small, circular piece of DNA that can be transferred between bacteria

Plasmids can pass through the pilus into the recipient bacterium’s genome.

Question 14

Fill in the blank: The process by which bacteria swap DNA is called _______.

Answer 14

[conjugation]

Question 15

True or False: Bacteria reproduce by binary fission and can exchange DNA with other bacteria.

Answer 15

True

Bacteria reproduce asexually but can still exchange genetic material.

Question 16

What is the primary method of reproduction for most eukaryotic organisms?

Answer 16

Sexual reproduction

This involves the mixing of DNA from each parent through specialized cells called gametes.

Question 17

What are gametes?

Answer 17

Specialized cells used in sexual reproduction

Gametes are responsible for combining genetic material from two parents.

Question 18

What is the chromosome number of haploid gametes?

Answer 18

One-half the number of chromosomes contained in diploid cells

This is essential for maintaining the chromosome number across generations.

Question 19

How are haploid gametes produced?

Answer 19

Through specialized cell division known as meiosis

Meiosis occurs in the gonads.

Question 20

Fill in the blank: Gametes are usually _______.

Answer 20

haploid

Question 21

True or False: Gametes are diploid cells.

Answer 21

False

Gametes are haploid, which is essential for sexual reproduction.

Question 22

What is the primary reproductive strategy of most multicellular organisms?

Answer 22

Sexual reproduction

Most vertebrate species also reproduce sexually.

Question 23

Why is sexual reproduction considered adaptive despite reducing genes in offspring?

Answer 23

It allows for elimination of harmful mutations

This helps prevent the accumulation of harmful mutations over generations.

Question 24

What is one potential benefit of sexual reproduction related to gene combinations?

Answer 24

It may generate beneficial gene combinations

This is particularly useful for immunity against evolving parasites.

Question 25

What hypothesis explains the advantage of sexual reproduction in relation to parasites?

Answer 25

The Red Queen hypothesis ## Footnote This hypothesis suggests that constant adaptation is necessary to survive against evolving threats.

Question 26

How can certain gene combinations aid organisms?

Answer 26

They may be better for dealing with changing environments ## Footnote This adaptability is crucial for survival in fluctuating conditions.

Question 27

What is Sequential Hermaphroditism?

Answer 27

A process where an organism begins as one sex and changes to another as an adult ## Footnote This involves changes in gonadal type/function, dominant steroid secreted, morphology, and behavior.

Question 28

What is Protogynous hermaphroditism?

Answer 28

A type of sequential hermaphroditism where an organism changes from female to male ## Footnote Example: striped parrot fish start as females and later become males.

Question 29

Give an example of a protogynous organism.

Answer 29

Striped parrot fish ## Footnote They start as females with bold stripes and small territories, later changing color and defending larger territories.

Question 30

What is Protandrous hermaphroditism?

Answer 30

A type of sequential hermaphroditism where an organism changes from male to female ## Footnote Example: male clownfish can become female if their mate dies.

Question 31

What happens to male clownfish if their mate dies?

Answer 31

The oldest juvenile grows rapidly to become the male mate ## Footnote This demonstrates protandrous hermaphroditism.

Question 32

True or False: Sequential hermaphroditism can be influenced by hormone injections.

Answer 32

True ## Footnote Hormone injections can counteract the natural process of sex change.

Question 33

What is sexual selection?

Answer 33

The evolution of sex differences (physical & behavioral) due to competition & choices related to mating & reproduction. ## Footnote Sexual selection is a key mechanism of evolution, influencing traits that improve mating success.

Question 34

According to Robert Trivers' Parental Investment Theory, which sex is usually pickier in mate selection?

Answer 34

The sex that invests the most in offspring, usually females. ## Footnote This theory highlights the relationship between parental investment and mating preferences.

Question 35

What are the different reproductive strategies of males and females?

Answer 35

Males often compete for access to females; females choose among many males based on anatomical features and behaviors. ## Footnote These strategies result in different evolutionary pressures on males and females.

Question 36

What physical traits do females often consider when choosing a mate?

Answer 36

Anatomical features such as fluctuating symmetry. ## Footnote Fluctuating symmetry is often perceived as an indicator of genetic fitness.

Question 37

What behavioral traits do females consider in mate selection?

Answer 37

Courtship behavior. ## Footnote Courtship behaviors can include displays, vocalizations, and other actions that signal fitness.

Question 38

True or False: Males are more likely to reproduce than females.

Answer 38

False. Males may compete for access to females but may never breed. ## Footnote This highlights the competitive nature of male reproductive strategies.

Question 39

Fill in the blank: According to sexual selection, males and females are exposed to different _______.

Answer 39

reproductive risks. ## Footnote These risks can influence their mating behaviors and strategies.