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MED-109 Biology II ✅ > Topic 9: Darwinian Theories ✅ > Flashcards

Topic 9: Darwinian Theories ✅ Flashcards

1
Q

When did Darwin publish his theory on The Origin of Species by Natural Selection?

A

1859

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2
Q

Evolution

A

The change in the inherited characteristics of biological populations over successive generations

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3
Q

The Origin of Species Theory

A

Evolution is defined as descent with modification

The mechanism of evolution is natural selection

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4
Q

The Origin of Species: the 2 main points

A
  1. Descent with modification (evolution)
  2. Natural selection is the mechanism of evolution (descent with modification)
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5
Q

Descent with modification

A

Evolution

-current species descended from ancestral species

-modification happened along the way

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6
Q

Natural selection is the mechanism of evolution

A

Individuals with favorables inherited traits are more likely to survive and reproduce
-survival of the fittest

Accumulation of these favorable heritable traits in a population over time=> higher proportion of individuals with better traits

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7
Q

Natural selection

A

Evolutionary process

Occurs when a population’s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others

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8
Q

Natural selection: step by step

A
  1. Populations with varied inherited traits
  2. Elimination of individuals with certain traits
  3. Reproduction of survivors
  4. Increasing frequency of traits that enhance survival and reproductive success
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9
Q

Artificial selection

A

Process of modification of other species by humans by selecting and breeding individuals with desired traits

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10
Q

Natural selection and adaptation

A

Darwin proposed that natural selection is the mechanism for evolutionary adaptation of populations to their environments

Natural selection: process in which individuals with favorable inherited traits are more likely to survive and reproduce

Adaptation: evolutionary processes that enhance the fitness and survival of individuals in their environment

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11
Q

Adaptation

A

Evolutionary processes

Enhance the fitness and survival of individuals in their environment

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12
Q

Natural Selection and Adaptation: what conclusions did Darwin draw?

A

Observation 1: Variation in a population

Observation 2: Overproduction of offspring

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13
Q

Observation 1

A

Variation in a population

-Members of a population often vary in their inherited traits

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14
Q

Observation 2

A

Overproduction of offspring

-All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce

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15
Q

Darwin’s Theory:Natural Selection and Adaptation

A

Observations:
1. Variations in the heritable characteristics of individuals in a population

  1. Overproduction of offspring: organisms produce more offspring than the environment can support

Conclusions:
1. Survival of the fittest- individuals that are well suited to their environment tend to leave more offspring than other individuals

  1. Adaptations in the population- over time, favorable traits accumulate in the population
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16
Q

What does Natural Selection NOT create?

A

New traits

It edits or selects for traits already present in the population

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17
Q

What does Adaptation depend on?

A

The local environment

It determines which traits will be selected for or against in any specific population

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18
Q

What do Adaptations vary with?

A

Adaptations vary with different environments

19
Q

Example of Natural Selection and Adaptation

A

Thalassaemia

Survival of thalassaemia allele heterozygous carriers in countries where malaria was endemic

Explanation:
Plasmodium malariae (the protist that causes malaria) replicates in mosquitoes which live in (sub-)tropical regions

-this microorganism infects RBC and digest haemoglobin

-heterozygous carriers of the thalassaemia allele have lower haemoglobin levels=> more resistant to Plasmodium infection

Natural selection favoured selective survival of carriers of the thalassaemia allele

20
Q

What is the cause of thalassaemia

A

Evolution

21
Q

Scientific evidence for evolution

A

New discoveries are filling gaps identified by Darwin in The Origin of Species

-direct observations

-homology

-the fossil record

-biogeography

22
Q

Direct observations of Evolutionary Change

A

-Natural selection in response to introduced plant species

-the evolution of drug-resistant bacteria

-the evolution of insecticide-resistant mosquitoes

-enhanced survival of thalassaemia carriers upon exposure to malaria

23
Q

The evolution of drug resistant bacteria

A

Bacteria have short generation times (can divide every 1-3 hours)

Allows rapid adaptive evolution (adaptation) of bacteria

Eg: development of antibiotic resistance

24
Q

Staphylococcus aureus

A

Bacterium

Responsible for wide range of human infections

-became resistant to penicillin in 1945, 2 years after it was first widely used

-became resistant to methicillin in 1961, 2 years after first widely used

25
Q

MRSA

A

Methicillin-resistant S. Aureus

Dangerous pathogenic strain

26
Q

Methicillin

A

A beta-Lactam antibiotic

-binds to and inhibits the enzyme transpeptidase

MecA gene

Natural selection: when exposed to methicillin, MRSA strains are more likely to survive and reproduce than non-resistant S. Aureus strains

-MRSA strains are now resistant to many antibiotics

27
Q

Transpeptidase

A

Responsible for the formation of peptidoglycan in the bacterial cell wall

28
Q

MecA gene

A

Encodes a protein that binds beta-Lactam antibiotics

=>transpeptidase remains active in the presence of beta-Lactam

=>prevents them from inhibiting cell wall synthesis

=>Antibiotic resistance development

29
Q

Evolution of insecticide -resistant mosquitoes

A

Development of resistance to insecticide DDT

Month 0- resistance 4%
Month 8- resistance 45%
Month 12- resistance 77%

30
Q

Homology

A

Similarity between different species that results from common ancestry

31
Q

Homology types

A

Anatomical homologies: similarities in anatomical features (homologous structures)

Molecular homology: similarities in genetic material

32
Q

Homologous structures

A

Anatomical similarities that represent variations on a structure present in a common ancestor

33
Q

Comparative embryology

A

Reveals anatomical homologies not visible in adult organisms

34
Q

Eg of molecular homologies

A

Genes shared among organisms were inherited from a common ancestor

35
Q

Eg of anatomical homologies

A

Vestigial structures

-organism structures that have lost all or most of their original function during the course of evolution

-remnants of features that served important functions in the organism’s ancestors

36
Q

Eg of vestigial structure

A

Human appendix

-from fully functional cecum to current human appendix

Human ancestors ate more easily digested foods => became less reliant on cellulose-rich plants => cecum became less necessary

Mutations for small cecum size accumulated in human population => cecum continuously shrinking

Once necessary cecum degraded to current appendix

37
Q

Appendix

A

Dead-end pouch forming part of large intestine

Darwin suggested that the appendix was used for digesting leaves by herbivores

Herbivorous animals have a very long cecum that hosts bacteria to digest cellulose

38
Q

Evolution is the change in __1 of __2 over __3

A

Change in the 1(inherited characteristics) of 2(populations) over 3(successive generations)

39
Q

Regarding evolution; individuals do not evolve..

A

Populations evolve over time

40
Q

Darwins evolution theory

A

Descent with modification by natural selection

41
Q

Natural selection summary

A

Process in which individuals with favorable inherited traits are more likely to survive and reproduce

It is the mechanism for adaptation => increases the adaptation of organisms to their environment over time

42
Q

Adaptation summary

A

If the environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species

43
Q

What effect can Natural Selection have on heritable traits that vary in a population?

A

Can only increase or decrease

44
Q

Overview of Natural Selection and Adaptation

A

Population of Organisms

→Hereditary variations
→Overproduction and struggle for existence

→Differences in reproductive success

→Evolution of adaptions in the population

MED-109 Biology II ✅ (9 decks)

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