Chapter 22: Introduction to Evolution (Part 2, Week 1) Flashcards
[The molecular processes that underlie evolution] What can researchers in evolutionary biology now analzye, with the advent of molecular approaches, to see associated changes?
They can analyze how changes in genetic material are associated with changes in phenotype.
Phenotypes are the set of observable characteristics or traits of an organism.
What are two or more genes derived from the same ancestral gene that have accumalated random mutations that make their sequences slightly different?
Homologous genes.
What do you call homologous genes found in different species?
Orthologs
Orthologs have similar gene sequences because they are derived from the same ancestral gene. The sequences are not identical because after the species diverged, each one accumulated different random mutations that changed their sequences.
Example: Consider a gene that encodes a transport protein involved in the uptake of metal ions into the cells of two different species of bacteria.
- Millions of years ago, the two species of bacteria had a common ancestor.
- This common ancestor diverged into two different species, eventually evolving into E.coli, C. cac, and many other species.
- Since the divergence, the gene encoding the transport protein has accumlated mutations that altered its sequence, though the similarity between E. coli and C. cac genes remain striking.
- The two sequneces are similar because they were derived from the same ancestral gene, but they are not identical due to the independent accumlation of different random mutations.
What are two or more homologous genes within a single species termed?
Paralogs
What is a group of homologous genes within a single species that carry out related functions?
Gene family
What is an example of a well-studied gene family in humans?
The globin gene family.
Comprised of 14 genes on three different chromosomes that are hypothesized to be derived from a single ancestral globin gene.
The advantages of gene families, in the care of globin, play a role in oxygen binding and allows these globin genes to be expressed at different stages of development during the embryonic, fetal, and postpartum stages of life.
For adaptation, these gene families have allowed terristial mammals to use internal gestation to protect their young instead of laying eggs like reptiles. The embryonic and fetal forms of hemoglobin allow the embryo and fetus to capture oxygen from the bloodstream of the mother.
What is a type of evolution in which genetic changes occur in a series of related species that form a lineage; species evolve from pre-existing species by the accumulation of mutations?
Vertical evolution (gene duplications and gene mutations)
What is a process in which an organism incorporates genetic material from another organism without being the offspring of that organism?
Horizontal gene transfer
Give an example of horizontal gene transfer?
Hint: Paramecium (eukaryotic microorganism)
- The paramecium engulfs a bacterial cell and degrades it in a phagocytic vesicle.
- A bacterial gene escapes to the nucleus of the host paramecium where it is inserted into one of the chromosomes.
- This gene has now transferred from a bacterial species to an eukaryotic species. By analyzing gene sequences of many different species, researches have discovered that horizontal gene transfer is a common phenomenon.
What are the three mechanisms of gene transfer that could result in horizontal gene transfer between two different bacterial species?
Conjugation, transformation, and transduction.
Conjugation - direct contact between a donor cell, who sends a plasmid, to a recipient cell that now has a plasmid.
Transformation - a fragment of DNA from a donor cell is released into the environment. This DNA fragment is taken up by a recipient cell, which incorporates the DNA into its chromosome.
Transduction - when a bacteriophage infects a donor cell, it causes the bacterial chromosome of the donor cell to break up into fragments. A fragment of bacterial chromosomal DNA is incorporated into a newly made bacteriophage. This bacteriophage then transfers this fragement of DNA to a recipient cell.
What percentage of variation in the genetic composition of modern bacterial species can be attributed to the process of horizontal gene transfer?
20-30%
These gene transfers are varied but most of them affect survival and reproduction (conferring antibiotic resistance, ability to degrade toxic compounds, and pathogenicity (ability to cause disease))
Other than vertical evolution and horizontal gene transfer, what other changes can affect evolution?
Changes in chromosome structure and number.
Comparisons of chromosomes of closely related species have revealed that changes in chromosome structure and/or number are common.
Fun fact: What is interesting about chromosome 2?
Humans have only one large chromosome 2 (second largest; 8% of total DNA) and is a result of an end to end fusion of two ancestral chromosomes.
Also, because of this, humans have 23 pairs of chromosomes while other hominidae have 24 pairs.
Review Concept Questions:
Heritable change in traits of a population from one generation to the next is called ______.
Evolution
Small-scale changes in a single gene or allele frequencies of a population are termed _______ , whereas large-scale patterns such as the formation of new species are referred to as __________
Microevolution and macroevolution
A group of related organisms that share a distinctive form constitute a(n) _______
species
Evolution is supported by a substantial body of evidence and explains a wide range of observations; thus it is considered a scientific ________
theory
Some scientists believe that nothing in biology makes sense unless viewed in the light of the theory of evolution; why?
Evolution provides a framework for understanding all of the diversity of life on Earth.
When did European scholars first begin to apply empirical and scientific thought to their study of biological phenomena?
The 1600s
A change in the allele frequencies of a population over three generations is an example of ______.
microevolution
Which observation was the basis of John Ray’s concept of a species?
Individuals of one species do not interbreed with individuals of another species.
Which of the following statements is typically used as a working definition of species?
A group of related individuals that share a distinctive form.
Why is evolution considered a theory? (2)
Because it is supported by a large body of evidence
Because it helps explain a very wide range of observations
The scientist who recorded information about the natural world on the voyage of the HMS Beagle and developed a theory that existing species have evolved from pre-existing species was __________ __________.
Charles Darwin
Why is the theory of evolution a unifying theme in biology?
It explains the diversity of life.
Individuals with heritable traits that make them better suited to their native environment tend to flourish and reproduce more than others. This process is called ______.
Natural Selection
In the 1600s, ideas about the living world dramatically changed as scholars developed the basis of ______.
empirical and scientific thinking
According to Darwin’s ideas, two factors interact to bring about evolutionary change: genetic change and __________ __________.
genetic change; natural selection
What scientist was influenced by Malthus’ paper and played a key role in developing the theory that existing species evolve from pre-existing species?
Charles Darwin
What is one type of genetic change that can lead to variation in a heritable trait among a species?
Gene mutation
Some of the offspring produced by each generation may not survive and reproduce because ______.
resources are often limited
Shell size and shape in a species of snail varies, with two shapes being most common: thin walled with a pointed spire, and thick walled with a low, rounded spire. If a species of crab that eats snails by crushing their shells moves into an area with roughly equal numbers of snails with the two shell shapes, what do you predict will happen over the course of the next 50 generations of snails?
Thick-shelled snails will survive better and leave more offspring, and will become more numerous in the population.
Prior to the development of tools to analyze DNA and protein sequences, which of the following provided evidence of biological evolution?
The fossil record, Distribution of related species, Selective breeding experiments, Comparative anatomy
Darwin’s observation that there were Patagonian hares but no rabbits in South America would be considered ______ evidence of evolution.
biogeographical
Not all of the offspring produced by an organism survive and reproduce. Why?
Organisms produce more offspring than the environment can support.
Environmental resources are often limited.
The study of the geographic distribution of modern and extinct species is called _________
biogeography
_______ evolution occurs when two species from different lineages independently evolve similar characteristics because they occupy similar environments.
Convergent
Recently, what type of evidence has allowed biologists more insight into how genetic changes relate to the evolution of new species?
Molecular
All of the following can provide evidence of biological evolution EXCEPT ______.
Reproduction. The fact that organisms reproduce is NOT evidence for evolution.
The giant anteater is a(n) _________ mammal, whereas the echidna is a(n) _______ mammal.
placental. egg laying
T/F: Even though the fossil record is still incomplete, there are many examples where fossils provide information on the evolution of a series of related organisms.
True
The long snouts and tongues of the giant anteater from South America and the echidna from Australia are an example of convergent evolution because
similar structures evolved in lineages that are independent (not closely related).
The anteater and the echidna have very similar snouts adapted for eating ants, yet those two species are not closely related; their similar snouts are called
analogous structures.
When two species from different lineages independently evolve similar characteristics because they occupy similar environments, then what has occurred?
Convergent evolution
Programs and procedures that involve choosing parents with particular characteristics to mate and produce offspring with desirable traits are described by the term ________ __________.
Selective or artificial; breeding or selection
In biology, the term ________ refers to a similarity that occurs due to descent from a common ancestor.
Homology
The giant anteater, a placental mammal from South America, and the echidna, a marsupial from Australia, have similar long snouts and tongue; this is an example of
convergent evolution.
Modern vertebrates, such as humans, bats, and whales, have forelimbs that contain the same set of bones from a common ancestor, but that have undergone independent evolutionary changes in each lineage. These are best described as ______ structures.
homologous
Similar characteristics that have arisen independently in unrelated species that occupy similar environments are called ________ structures or convergent traits.
Analogous
Evolutionary theory can explain _________ structures, which are functional anatomical structures in related organisms that are similar based on their origin from a common ancestor.
Homologous
Two or more genes derived from the same ancestral gene are called _________ genes.
Homologous
Which of the following terms indicates similarity due to a common origin?
Homology
Genes in different species that arose from the same gene in the immediate ancestor of the two species are said to be ________. These genes are not identical due to the independent accumulation of random mutations.
Orthologs
Two or more homologous genes found in the same species are known as _______.
paralogs or paralogous
The forelimbs of modern vertebrate species are an example of what? (2)
Homologous structures
Anatomical homologies
As genetic material is transferred from one generation to the next, genetic changes accumulate over a number of generations due to mutations, gene duplications, and exon shuffling and may result in new species from an ancestor, which is known as ______.
Vertical evolution
Structures that are similar to each other because they are derived from a common ancestor are called ______ structures.
homologous
Not analogous because this is similarity due to independent evolution of similar traits in two unrelated organisms.
In general, when two or more genes are found to be derived from a common ancestor gene, they are referred to as ______.
Homologous genes.
No. Paralogs are a special case of homologous genes.
No. Orthologs are a special case of homologous genes.
In general, when two or more genes are found to be derived from a common ancestor gene, they are referred to as ______.
Homologous genes.
No. Paralogs are a special case of homologous genes. (2 or more homologous genes in a single species)
No. Orthologs are a special case of homologous genes. (homologous genes found in different species)
No, Analogs are genes that evolved independently but code for similar proteins
How can species acquire new genes? (3)
Gene duplication
Horizontal gene transfer
Random mutations
Orthologs are homologous genes in different species as a result of ______.
random mutations over time
Which of the following are examples of evolution at the genome level? (2)
Chromosome duplication
Chromosome inversion
When genetic material is transferred from one organism to another organism that is not its offspring, it is known as ______.
horizontal gene transfer
A species may acquire new genetic variation via several ways. These include _________ within pre-existing genes, gene ____________ that produce gene families, and ___________ gene transfer.
mutation, duplication, and horizontal gene transfer
Genes in different species that arose from the same gene in the immediate ancestor of the two species are said to be _______. These genes are not identical due to the independent accumulation of random mutations.
Orthologs
Evolution at the ______ level can involve changes in chromosome structure and number.
genomic
