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Plant Biology > Unit 3 > Flashcards

Unit 3 Flashcards

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1
Q

In 300 BC, it was thought that…

A

Life forms are permanent and unchanging

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2
Q

In the 1600’s, the date of creation was taken from…

A

the Bible (4004 BC).

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3
Q

In the 1800’s, it was discovered that…

A

Earth’s geological phenomena are due to gradual natural causes that we can still observe. Therefore Earth must be millions of years old. Current estimates > 4 billion.

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4
Q

Before Darwin, who suggested that species evolve?

A

Charles Lyell, Erasmus Darwin and Jean Baptiste Lamarck

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5
Q

What did Larmack propose?

A

an evolutionary mechanism: species adapt to their environment
- Traits change through use or disuse
- Acquired changes are passed on to offspring

*no evidence to support inheritance of acquired traits

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6
Q

Explain Darwin’s observations of the cacti on the Galapagos islands…

A

Cacti on the Galápagos Islands with tortoises were
taller than those on other islands because the tallest
cacti were less likely to be completely eaten, and
therefore left more descendants

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7
Q

Explain the three premisses of which the theory of evolution by natural selection rests…

A

Darwin realized natural selection is the mechanism by which populations adapt to their environment. The concept of natural selection rests on three premises:
1. Every species is capable of producing more offspring than can survive or reproduce
2. Individuals in a population have heritable variation in traits affecting their chances for survival or reproduction
3. Individuals with the most advantageous traits will
produce the most offspring

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8
Q

Define evolution…

A
  • Cumulative change in the genetic characteristics of a population or species through time
  • Change in allele or genotype frequency over time
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9
Q

Define natural selection…

A

The process by which the genotypes genetically best
suited to survive and reproduce in a particular
environment give rise to a disproportionate share of the offspring and so gradually increase the overall ability of the population to survive

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10
Q

Explain the premises by which evolution by artificial selection rests…

A

Darwin realized natural selection is the mechanism by which populations adapt to their environment. Artificial selection works in a similar way:
1. Species are capable of producing more offspring than humans choose for further breeding
2. Individuals in a population have heritable variation in traits affecting their chances of being chosen.
3. Humans ensure that individuals with the most
advantageous traits will produce the most offspring

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11
Q

Natural selection is ____ ______ ________ of evolution.

A

only one mechanism
*Natural selection ≠ Evolution

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12
Q

What forces lead to evolutionary change?

A
  • Mutation
  • Genetic drift
  • Natural selection
  • Non-random mating
  • Migration
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13
Q

Define genotype frequency…

A
  • Proportion of a population with a certain genotype
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14
Q

Define allele frequency…

A
  • Proportion of gene copies of a certain type (allele) in the population
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15
Q

Define population…

A

All individuals of a certain species living in a particular area

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16
Q

Define polymorphic…

A

Multiple different alleles at a locus

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17
Q

Explain the process of predicting phenotypes and genotypes.

A

True breeding lines are crossed
(PP and pp) —>
All F1 have purple phenotype
(genotype is Pp) —>
Cross (or self) F1s
(Pp and Pp) —>
F2 show 3:1 purple:white phenotype
F2 show 1 PP : 2 Pp : 1 pp genotype

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18
Q

Define locus…

A

the position of a gene on a chromosome

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19
Q

Define allele…

A

any of the alternative forms of a given gene (P or p)

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20
Q

Define genotype…

A

the genetic constitution of an organism (PP, Pp, pp)

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21
Q

Define phenotype…

A

the observable trait (purple or white flower)

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22
Q

What is a mutation?

A
  • Mutation is the ultimate source of all heritable variation in evolution
  • Any change in the DNA of an organism
  • Mutations occur randomly as a result of mistakes in
    replication or during crossing over
  • Mutations can be induced by chemicals or radiation
  • Only mutations that occur in reproductive cells are
    heritable
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23
Q

Explain the types of mutation…

A

Substitution (cta –> cAa)
Insertion (cat –> caGt)
Deletion (cat –> c-t)

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24
Q

Explain the affects of mutation on phenotype…

A
  • In plants and animals, most mutations have little or no effect on phenotype
  • When there is a phenotypic effect, it is usually bad
  • Occasionally, mutations have a good effect on
    phenotype
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25
Q

Explain the relation between mutation and evolution…

A
  • Mutation is the ultimate source of all heritable variation in evolution
  • Point mutations at a site are rare: about 1 in a billion
  • Therefore (on their own) new mutations do not change allele frequencies much
  • When populations are extremely large: most possible mutations might occur somewhere
26
Q

Define random genetic drift…

A

Random changes in allele frequency
*Chance events can lead to large changes in allele
or genotype frequency when populations are small
*this is NOT natural selection

27
Q

Explain past genetic drift: the founder effect

A
  • Colonization of new area by a small part of original population
  • Causes reduced genetic variability
    *Yellowish flowers (with R 1) could have survived just as well.. this is not natural selection
28
Q

Define fitness…

A

The ability of an organism to… survive and transmit its alleles to the next generation

29
Q

What are the components of fitness?

A
  • Viability: Survivorship from fert. to repro.
  • Fecundity: The # of offspring produced
  • Viability and fecundity lead to # of alleles transmitted to the next generation
    *More alleles contributed = Higher fitness
  • this leads to adaptation = the process by which a population changes phenotype to one that better fits the present environment
30
Q

What was Mendel’s first law?

A

law of segregation: Two alleles at a locus segregate
into separate gametes: half carrying one allele and the other half the other

31
Q

Explain directional selection…

A

Individuals with an extreme phenotype are… favored over individuals at the other extreme
Example: Weedy plants on islands
- Dispersal –> “drowning”
- Strong selection against dispersal

32
Q

Explain stabilizing selection…

A

Stabilizing Selection: Favors individuals with… intermediate phenotypes
- Results in a narrowing of
phenotypic distribution
- Avg value remains
unchanged

33
Q

Explain disruptive selection…

A

Disruptive Selection: Intermediate trait values are
disfavored, extremes favored
- Results in: Phenotypic divergence

34
Q

Define outbreeding…

A

mating between distantly related parents

35
Q

Define migration…

A

movement of individuals from one population
to another

36
Q

Define gene flow…

A

movement of alleles from one population to
another through mating

37
Q

Define hybridization…

A

movement of alleles from one species to another. Hybridization is not very common.

38
Q

What happens when there is no gene flow?

A

Populations diverge until they are too different genetically, phenotypically or ecologically to mate: Speciation

39
Q

Explain convergent evolution…

A

Adaptation to similar environments can cause unrelated species to evolve similar traits

40
Q

Explain morphological species concept

A

Organisms are considered members of the same species if they are highly similar in morphology (appearance)
*early taxonomists

41
Q

Explain the biological species concept

A

Species are groups of interbreeding natural populations that are reproductively isolated from other such groups

42
Q

What are some problems with the biological species concept?

A
  • Does not apply to asexual organisms, which include
    many microbes and some plants
  • Difficult to apply or test
  • Hybridization: many species (especially plants) can
    interbreed at least a little with other species
    *That is why scientists also use many other species
    concepts
43
Q

Define allopatric variation…

A

geographic isolation resulting in genetic divergence

44
Q

Define sympatric variation…

A

genetic divergence without geographic isolation

45
Q

Examples of geographic variation include…

A
  • Formation of new islands
  • Examples of geographic barriers
  • Recession of glaciers
  • Fragmentation of habitat
  • Drying down of a water body
46
Q

Explain polyploidy…

A

Polyploids contain more than 2 sets of chromosomes
- Found in some animals
- Very common in plants
- In some tissues e.g. liver cells of mammals, endosperm of plants

47
Q

Most crops are ________.

A

polyploidy

48
Q

Polyploid plants have _______ ______ and tend to be _______ plants.

A

larger cells; larger

49
Q

Explain sympatric speciation via polyploidy…

A

Two distinct species produce a fertile hybrid with increased ploidy – it cannot mate with either parent species so a new species has formed

50
Q

Define allopolyploidy…

A

two distinct species produce a fertile hybrid with increased ploidy

51
Q

Define autopolyploidy…

A

Chromosome doubling within a species

52
Q

Explain the process of allopolyploidy…

A
  • Two species cross
  • Pairing problems during meiosis in hybrid
  • Chance chromosome doubling
  • Every chromosome now has a partner
  • Fertility is restored
    *The allopolyploid has more chromosomes than parents, so crossing with parent species leads to sterile offspring (problems pairing in meiosis)
53
Q

Explain the process of autopolyploidy…

A
  • Nondisjunction in meiosis
  • Diploid gametes fuse —> Tetraploid (4N)
    *The tetraploid cannot exchange genes with the diploids because: Offspring will have odd number
    of chromosomes so pairing in meiosis fails
54
Q

What is allopatric speciation?

A

Allopatric speciation
* species diverge when separated by geographic
barriers

55
Q

What falls under sympatric speciation?

A

Sympatric speciation
* Allopolyploidy
* Autopolyploidy
* Other mechanisms e.g. non-random mating,
ecological isolation, disruptive selection

56
Q

Define taxonomy…

A

the branch of science concerned with classification, especially of organisms; systematics.

57
Q

Explain how to write scientific names…

A

There is a correct way to write scientific names. It follows a ranked system developed by botanist, Carl Linnaeus in 1700s:
1. Every species has a unique name.
2. All names follow a two-word (binomial) convention.
- Generic name (noun)
- specific epithet (adjective)
–> Conveys info about the spp.
3. Names are in Latin. –> non-changing

58
Q

Define phylogenetics…

A

the study of evolutionary relationships among species

59
Q

Define morphology…

A

the physical structure of an organism
* Morphology is strongly affected by natural selection to fit the organism’s environment

60
Q

DNA sequence is better for phylogenetics because…

A
  • The discovery of protein and DNA sequences showed that some proteins and their genes changed extremely slowly.
  • Their differences reflect degrees of relatedness.

Plant Biology (3 decks)

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