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Evolution & the Origin of Species Flashcards

Chapter 18 of the book

1
Q

All organisms are products of what?

A

Evolution adapted to their environment.

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2
Q

Is evolution an ongoing process?

A

Yes, all living organisms evolved at some point from a different species.

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3
Q

What is the Theory of Evolution?

A

The unifying theory of biology, meaning it is the framework within which biologists ask questions about living world.

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4
Q

What is the power of the Theory of Evolution?

A

It provides direction for predictions about living things that are borne out in ongoing experiments.

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5
Q

What is the foundation from which we approach all questions in biology?

A

All life has evolved & diversified from a common ancestor.

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6
Q

Evolution by natural selection…

A

describes a mechanism for how species change over time.

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7
Q

This mechanism is now referred to as what?

A

An inheritance of acquired characteristics by which the environment causes modifications in an individual, or offspring could use or disuse of a structure during its lifetime, & thus bring about change in a species.

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8
Q

What 2 naturalists independently conceived & described the actual mechanism for evolution?

A

Charles Darwin & Alfred Russel Wallace. Each naturalist spent time exploring the natural world on expeditions to the tropics.

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9
Q

What islands did Darwin observe species of organism that were similar, yet had distinct differences?

A

The Galapagos Islands west of Ecuador.

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10
Q

What is Natural Selection?

A

A.K.A “survival of the fittest,” is the more prolific reproduction of individuals with favorable traits that survive environmental changes b/c of those traits. This leads to evolutionary change.

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11
Q

Natural Selection was an inevitable outcome of what 3 principles that operated in nature?

A
  1. Most characteristics of organisms are inherited, or passed from parent to offspring.
  2. More offspring are reproduced than are able to survive, so resources for survival & reproduction are limited. The capacity for reproduction in all organisms outstrips the availability of resources to support their #s. Thus, there is competition for those resources in each generation.
  3. Offspring vary among each other in regard to their characteristics & those variations are inherited.
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12
Q

Offspring with inherited characteristics allow them to best compete for limited resources will survive & have more offspring than those individuals with variations that are less able to compete because, why?

A

B/c characteristics are inherited, these traits will be better represented in the next generation. This will lead to changes in pop. over generations in a process called Descent With Modification.

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13
Q

Natural Selection leads to what?

A

Greater adaptation of the pop. to its local environment.

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14
Q

What is the only mechanism known for adaptive evolution?

A

Natural Selection

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15
Q

When can natural selection only take place?

A

If there is variation, or differences, among individuals in a population. These differences must have some genetic basis.

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16
Q

Genetic Diversity in a pop. comes from what 2 main mechanisms?

A
  1. Mutation
  2. Sexual Reproduction
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17
Q

What is a Mutation?

A

A change in DNA, is the ultimate source of new alleles, or new genetic variation in any pop.

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18
Q

How does a Mutation affect an organism’s phenotype?

A

By giving it reduced fitness (lower likelihood of survival or fewer offspring), beneficial fitness, or no effect on fitness (Neutral mutations).
Mutations may have a whole range of effect sizes on the organism’s fitness that expresses them in their phenotype, from a small effect to a great effect.

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19
Q

What is sexual Reproduction?

A

When 2 parents reproduce, unique combinations of alleles assemble to produce the unique genotypes & thus phenotypes in each offspring.

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20
Q

What is an adaptation?

A

A heritable trait that helps an organism’s survival & reproduction in its present environment.

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21
Q

What does “fit” mean?

A

Groups of organisms adapt to their environment when a genetic variation occurs over time that increases or maintains the population to its environment.

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22
Q

Whether or not a trait is favorable depends on what?

A

The current environmental conditions.

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23
Q

Are the same traits always selected?

A

No, because environmental conditions can change.

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24
Q

What has the evolution of species resulted in?

A

Enormous variation in form & function. Evolution gives rise to groups of organisms that become tremendously different from each other.

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25
What is Divergent Evolution?
2 species that evolve in diverse directions from a common point. Example: Reproductive organs of flowering plants. They share the same basic anatomies; however, they look very different as a result of selection in different physical environments & adaptation to different kinds of pollinators.
26
What is Convergent Evolution?
Where similar traits evolve independently in species that do NOT share a common ancestry. Example: Bat & insect wings have evolved from very different original structures. Both came to the same function, flying, BUT did so separately from each other.
27
What does Natural selection act on?
Individual organisms, which can then shape entire species.
28
What are the 4 pieces of evidence for evolution?
1. Fossils 2. Anatomy & Embryology 3. Biogeography 4. Molecular Biology
29
How does Fossils provide evidence?
That organisms from the past are not the same as those today, & fossils show a progression of evolution.
30
How does Anatomy provide evidence?
By showing the presence of structures in organisms that share the same basic form. Example: Bones in human, dog, bird, & whale appendages all share the same overall construction resulting from their origin in a common ancestor's appendages.
31
What are homologous structures?
Changes in the bones' shapes & sizes in different species, but they have maintained the same overall layout. (synonymous parts)
32
What are vestigial structures?
An unused structure that exists in an organism that has no apparent function at all, & appears to be residual parts from a past common ancestor.
33
What are analogous structures?
When similar characteristics occur b/c of environmental constraints & not due to a close evolutionary relationship, it is an analogy or homoplasy.
34
What is the convergence of form in organisms that share similar environments?
These similarities occur not b/c of common ancestry, BUT b/c of similar selection pressures.
35
What is Embryology?
The study of the anatomy of an organism's development to its adult form.
36
How does Embryology provide evidence?
Of relatedness b/w now widely Divergent groups of organisms.
37
How does Biogeography provide evidence?
The geographic distribution of organisms on the planet follows patterns that we can explain best by evolution in conjunction with tectonic plate movement over geological time. Groups that evolved since the breakup appear uniquely in regions of the planet.
38
How does molecular biology provide evidence?
The molecular structures of life reflect descent with modifications. DNA's universality reflects evidence of a common ancestor for all of life. Fundamental divisions in life b/w the genetic code, DNA replication, & expression are reflected in major structural differences. In general, the relatedness of groups of organisms is reflected in the similarity of their DNA sequences. DNA sequences have also shed light on some of the mechanism
39
What are the Misconceptions of Evolution?
1. Evolution Is Just A Theory 2. Individuals Evolve 3. Evolution Explains the Origins of Life 4. organisms Evolve on Purpose
40
Explain the "Evolution Is Just a Theory" misconception.
Purposefully misusing the term "theory," a body of thoroughly tested & verified explanations for a set of observations of the natural world (which describes understood facts about the world), by stating it is a guess or suggested explanation (however this def. is more like a hypothesis). By doing so they are implying that there is little evidence supporting it & that it is still in the process of rigorous testing. This is MISCHARACTERIZATION.
41
Explain "Individuals Evolve" misconception.
Individuals do change over their lifetime but this is development & involves changes programmed by the set of genes the individual acquired at birth in coordination with the individual's environment. They do NOT evolve, this would occur in a pop. over time.
42
Explain "Evolution Explains the Origin of Life" misconception.
The Theory of evolution Explains how pop. change over time & how life diversifies the Origin of species. It does NOT shed light on the beginnings of life, like the origins of the first cells.
43
Explain "Organisms Evolve on Purpose" misconception.
That a pop. evolves in response to a changing environment & evolution is somehow intentional. However in actuality a changed environment results in some individuals in the pop., those with particular phenotypes. Also the variation that natural selection works on is already in a pop. & does NOT arise in response to an environmental change.
44
Why is evolution NOT a directed goal?
Species do not become "better" over time. They simply track their changing environment with adaptions that maximize their reproduction in a particular environment at a particular time. What characteristics evolve in a species are a function of the variation present & the environment.
45
What is a species?
A group of individual organisms that interbreed & produce fertile, viable offspring.
46
Members of the same species share both external & internal characteristics, which develop from what?
Their DNA. The closer relationship 2 organisms share, the more DNA they have in common. Organisms of the same species have the highest level of DNA alignment & therefore share characteristics & behaviors that lead to successful reproduction.
47
What is a hybrid?
A cross b/w 2 species (most likely infertile).
48
What is a gene pool?
A collection of all the gene variants in the species. Populations of species share a gene pool.
49
The basis to any changes in a group or pop. of organisms must be what?
Genetic b/c this is the only way to share & pass on traits.
50
When variations occur with in a species, they can only pass to the next generation along what 2 main pathways?
1. Asexual Reproduction 2. Sexual Reproduction
51
How does the change pass asexually?
Simply if the reproducing cell possess the changed trait.
52
How does the change pass sexually?
A gamete must posses the changed trait. Sexually-reproducing organisms can experience several genetic changes in their body cells, but if these changes do NOT occur in a gamete, the changed trait will never reach the next generation. ONLY heritable traits can evolve.
53
What is speciation?
The formation of 2 species from 1 original species. As 1 species changes over time, it branches to form more than 1 new species, repeatedly, as long as the pop. survives or until the organism become extinct.
54
For speciation to occur, what must happen?
2 new pop. must form from 1 original pop. & they must evolve in such a way that it becomes impossible for individuals from the 2 new pop to interbreed.
55
What is Allopatric Speciation?
Involves geographic separation of pop. from a parent species & subsequent evolution.
56
What is Sympatric Speciation?
Involves separation occurring with a parent species remaining in one location.
57
What is gene flow?
The movement of alleles across a species' range. Individuals move & then mate with individuals in their new location.
58
What prevents alleles' free-flow?
When pop. become geographically discontinuous. When that separation lasts for a period of time, the 2 pop. are able to evolve along different trajectories. Typically, environmental conditions will differ causing natural selection to favor divergent adaptations in each group.
59
Can isolation of populations leading to Allopatric Speciation occur in a variety of ways?
Yes, it depends entirely on the organism's biology & its potential for dispersal.
60
What 2 categories does allopatric process into?
1. Dispersal 2. Vicariance
61
What is Dispersal?
When a few members of a species move to a new geographical area.
62
What is Vicariance?
When a natural situation arises to physically divide organisms.
63
When is it more likely for speciation to occur?
The further the distance b/w 2 groups that once were the same species. This seems logical b/c as the distance increases, the various environmental factors would likely have less in common than locations in close proximity.
64
What is adaptive radiation?
Many adaptations evolve from a single point of origin; thus causing the species to radiate into several new ones. A pop. of 1 species disperses throughout an area, & each finds a distinct niche or isolated habitat. Over time, the varied demands of their new lifestyles lead to multiple speciation events originating from a single species.
65
Can divergence occur if no physical barriers are in place to separate individuals who continue to live & reproduce in the same habitat?
Yes, this is called sympatric, the process of speciation within the same space.
66
What is one form of sympatric speciation?
A serious chromosomal error during cell division.
67
What is aneuploidy?
Sometimes the pairs (chromosome) separate & the cell end product has too many or too few individual chromosomes.
68
What is Polyploidy?
A condition in which a cell or organism has an extra set, or sets, of chromosomes. Results from an error in meiosis in which all of the chromosomes move into one cell instead of separating.
69
What are the 2 types of Polyploidy that can lead to reproductive isolation of an individual in the polyploidy state?
1. Autopolyploidy 2. Allopolyploid
70
What is autopolyploid?
A polyploid individual will have 2 or more complete sets of chromosomes from its own species.
71
What is allopolyploid?
When individuals of 2 different species reproduce to form a viable offspring.
72
Given enough time, the genetic & phenotypic divergence b/w pop. will affect what?
The characters that influence reproduction
73
Many types of diverging characters may affect what?
Reproductive Isolation
74
What is Reproductive Isolation?
The ability to interbreed, of the 2 pop. The inability to interbreed.
75
What ways/ 2 groups can Reproductive Isolation take place?
1. Prezygotic Barriers 2. Postzygotic Barriers
76
What is a prezygotic barrier?
A mechanism that blocks reproduction from taking place. Includes barriers that prevent fertilization when organisms attempt reproduction.
77
What is a postzygotic barrier?
Occurs after zygote formation. Includes organisms that don't survive the embryonic stage & those that are born sterile.
78
What is temporal isolation? (prezygotic barrier)
Differences in breeding schedules. Can act as a form of reproductive Isolation.
79
What is Habitat Isolation? (prezygotic barrier)
Pop. of a species move or are moved to a new habitat & take up residence in a place that no longer overlaps with the same species' other pop. Reproduction with the parent species ceases, & a new group exists that is now reproductively & genetically independent.
80
What is Behavioral Isolation? (prezygotic barrier)
When the presence of absence of a specific behavior prevents reproduction
81
What is a gametic Barrier? (prezygotic barrier)
Differences in their gamete cells prevent fertilization from taking place. For example, in some cases closely related organisms try to mate, but their Reproductive structures simply do not fit together.
82
What is Hybrid Inviability? (postzygotic barrier)
Hybrid individuals that cannot form normally in the womb & simply do not survive past the embryonic stage.
83
What is Hybrid Sterility? (postzygotic barrier)
The hybrid organism is unable to reproduce offspring of their own.
84
After speciation, two species may what?
Recombine or continue interacting indefinitely.
85
What is a Hybrid Zone?
2 closely related species continue to interact & reproduce, forming hybrids
86
What is Reinforcement?
Hybrids are less fit than either purebred species. The species continue to diverge until hybridization can no longer occur.
87
What is Fusion?
Reproductive barriers weaken until the 2 species become one.
88
What is stability?
Fit hybrids continue to be produced.
89
What are the 2 current patterns for speciation?
1. Gradual Speciation Model 2. Punctuated Equilibrium Model Both models suggest a father tempo, however they do not necessarily exclude gradualism.
90
What is the Gradual Speciation Model?
Species diverge gradually over time in small steps.
91
What is the Punctuated Equilibrium Model?
A new species undergoes changes quickly from the parent species, & then remains largely unchanged for long periods of time afterward.
92
What is the primary influencing factor on changes in speciation rate?
Environmental Conditions. Under some conditions, selection occurs quickly or radically.

Biology II (7 decks)

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