Lecture 2 Flashcards
What is evolution?
The change in the genetic composition of populations over time
This process involves changes in allele frequencies within a population.
What contributes to differences among individuals within a species?
Genetic, or heritable, differences
These differences can affect physical traits, behaviors, and other characteristics.
What does the process of natural selection predict about advantageous traits?
If a heritable trait confers an advantage, it will become more common over time
This process is a key mechanism of evolution.
What happens to disadvantageous traits according to natural selection?
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.
What are heritable traits encoded by?
Genes
Genes are functional linear stretches of deoxy-ribonucleic acid (DNA)
Where is DNA contained within an organism’s cells?
Chromosomes within the nucleus
The nucleus is a membrane-bound organelle that houses the cell’s genetic material.
How many genes does the human genome contain according to the Human Genome Project?
An estimated 20,000-25,000 genes
This estimate was provided in 2008.
What results from the interaction of genes with the environment over time?
Evolution
Evolution is the change in the heritable characteristics of biological populations over successive generations.
What is binary fission?
A method of reproduction where an organism splits in two
This method was used by the earliest known organisms with DNA.
What type of organisms were the earliest known to use DNA as a genetic repository?
Microscopic, single-celled organisms
These organisms reproduced by binary fission.
How do bacteria exchange DNA today?
Through a process called conjugation
This involves a hairlike tube called a pilus.
What is a pilus?
A hairlike tube that connects bacteria for DNA exchange
It is used during the process of conjugation.
What is a plasmid?
A small, circular piece of DNA that can be transferred between bacteria
Plasmids can pass through the pilus into the recipient bacterium’s genome.
Fill in the blank: The process by which bacteria swap DNA is called _______.
[conjugation]
True or False: Bacteria reproduce by binary fission and can exchange DNA with other bacteria.
True
Bacteria reproduce asexually but can still exchange genetic material.
What is the primary method of reproduction for most eukaryotic organisms?
Sexual reproduction
This involves the mixing of DNA from each parent through specialized cells called gametes.
What are gametes?
Specialized cells used in sexual reproduction
Gametes are responsible for combining genetic material from two parents.
What is the chromosome number of haploid gametes?
One-half the number of chromosomes contained in diploid cells
This is essential for maintaining the chromosome number across generations.
How are haploid gametes produced?
Through specialized cell division known as meiosis
Meiosis occurs in the gonads.
Fill in the blank: Gametes are usually _______.
haploid
True or False: Gametes are diploid cells.
False
Gametes are haploid, which is essential for sexual reproduction.
What is the primary reproductive strategy of most multicellular organisms?
Sexual reproduction
Most vertebrate species also reproduce sexually.
Why is sexual reproduction considered adaptive despite reducing genes in offspring?
It allows for elimination of harmful mutations
This helps prevent the accumulation of harmful mutations over generations.
What is one potential benefit of sexual reproduction related to gene combinations?
It may generate beneficial gene combinations
This is particularly useful for immunity against evolving parasites.
What hypothesis explains the advantage of sexual reproduction in relation to parasites?
The Red Queen hypothesis
This hypothesis suggests that constant adaptation is necessary to survive against evolving threats.
How can certain gene combinations aid organisms?
They may be better for dealing with changing environments
This adaptability is crucial for survival in fluctuating conditions.
What is Sequential Hermaphroditism?
A process where an organism begins as one sex and changes to another as an adult
This involves changes in gonadal type/function, dominant steroid secreted, morphology, and behavior.
What is Protogynous hermaphroditism?
A type of sequential hermaphroditism where an organism changes from female to male
Example: striped parrot fish start as females and later become males.
Give an example of a protogynous organism.
Striped parrot fish
They start as females with bold stripes and small territories, later changing color and defending larger territories.
What is Protandrous hermaphroditism?
A type of sequential hermaphroditism where an organism changes from male to female
Example: male clownfish can become female if their mate dies.
What happens to male clownfish if their mate dies?
The oldest juvenile grows rapidly to become the male mate
This demonstrates protandrous hermaphroditism.
True or False: Sequential hermaphroditism can be influenced by hormone injections.
True
Hormone injections can counteract the natural process of sex change.
What is sexual selection?
The evolution of sex differences (physical & behavioral) due to competition & choices related to mating & reproduction.
Sexual selection is a key mechanism of evolution, influencing traits that improve mating success.
According to Robert Trivers’ Parental Investment Theory, which sex is usually pickier in mate selection?
The sex that invests the most in offspring, usually females.
This theory highlights the relationship between parental investment and mating preferences.
What are the different reproductive strategies of males and females?
Males often compete for access to females; females choose among many males based on anatomical features and behaviors.
These strategies result in different evolutionary pressures on males and females.
What physical traits do females often consider when choosing a mate?
Anatomical features such as fluctuating symmetry.
Fluctuating symmetry is often perceived as an indicator of genetic fitness.
What behavioral traits do females consider in mate selection?
Courtship behavior.
Courtship behaviors can include displays, vocalizations, and other actions that signal fitness.
True or False: Males are more likely to reproduce than females.
False. Males may compete for access to females but may never breed.
This highlights the competitive nature of male reproductive strategies.
Fill in the blank: According to sexual selection, males and females are exposed to different _______.
reproductive risks.
These risks can influence their mating behaviors and strategies.
