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Life Science 142 > Lecture 1 > Flashcards

Lecture 1 Flashcards

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Biology 101 flashcards
1
Q

Explain fully where the earth started

A
  • Earth and other planets formed about 4.6 billion years ago
  • The earth cooled enough to form a crust 4.2 to 4.1 BYA. Surface temperature ranged from 500 to 1000deg Celsius
  • Earth originally had primitive atmosphere
    H2O, N2, CO2, H2 & CO were the gasses present.
  • It was a reducing atmosphere lacking free O2
  • The geological time scale in the next slide gives us a good idea of when life started and when oxygen was introduced into the atmosphere.
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2
Q

What did the presence of O2 inhibit

A

Formation of complex organic molecules

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3
Q

What is the central idea of biological evolution

A

All life on Earth shares a common ancestor

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4
Q

What is speciation

A
  • It is the splitting of one species in to two or more species, or the transformation of one species into a new species over time.
  • It is the final result of changes in the in gene pool allele and genotype frequencies
  • The one requires geographic isolation while the other one does not.
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5
Q

What are the 3 branches of speciation

A
  • Parapatry
  • Sympatry
  • Allopatry
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6
Q

Explain natural selection in evolution

A
  • The mechanism by which species change over time –some of this was discussed by Darwin
  • Inheritance of acquired characteristics-Lamarck is a name that comes to mind
    • This deals with modifications in an individual caused by its environment or disuse of a structure –it could be inherited by its offspring-causing a change in a species

eg ) Finches from Galapagos Archipelago

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7
Q

When can natural selection take place

A
  • Natural selection can only take place if there is variation among individuals in a population.
  • Genetic diversity in a population has two sources: Mutation and sexual reproduction
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8
Q

What are the patterns of evolution

A
  • Divergent evolution
  • Convergennt evolution
  • Analogous evolution
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9
Q

Source of a mutation

A
  1. A mutation can affect the phenotype that may cause reduced fitness- resulting in fewer offspring.
  2. Mutation may produce a phenotype with a beneficial effect on fitness
  3. Neutral mutations that have no effect on fitness
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10
Q

Explain homologous structures

A
  • Are related to each other through common descent but may differ in structure and function

e.g) the forelimbs of a horse and the wings of a bat

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11
Q

Explain analogous structures

A
  • Have the same function but not derived from the same organ in a common ancestor

e.g. the wings of an insect and the wings of a bat

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12
Q

What does homology indicate

A

Species belong to related group

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13
Q

What is evolution

A
  • The process that is responsible for the changes in characteristics of species and how new species arise
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14
Q

Explain parallel evolution

A
  • Produces similar characters in related lineages without occurring in a common ancestor
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15
Q

Explain convergent evolution fully

A
  • Similar biological traits evolves in two unrelated species as a result of exposure to similar environments. Eg Wings of birds and wings of bats
  • Acquisition of similar trait in distantly related lines of descent as a result of adaptation to similar environmental conditions
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16
Q

Explain adaptive radiation

A

When a single ancestral species rapidly gives rise to a radiation of new species as each adapts to a specific environment

Eg ) The Galapagos finches

17
Q

What is macroevolution

A
  • Is part of the history of life on earth and involves speciation
  • Speciation involves the splitting of one species into two or more species
18
Q

What are the 3 concepts of species

A
  • Morphological species concept
  • Evolutionary species concept
  • Phylogenetic species concept
19
Q

Explain each of the 3 concepts of species

A
  • Morphological species concept: Species identified on the basis of appearance or morphology
  • Evolutionary species concept: Species differentiated on the basis a specific evolutionary pathway
  • Phylogenetic species concept: A species is the smallest set of interbreeding organisms-usually a population, shares a common ancestor
20
Q

What are reproductive isolating mechanisms

A

Two major operators that makes sure that species remain separate

21
Q

Explain prezygotic isolators

A
  • Habitat isolation
  • Temporal – time differences in mating strategy
  • Behavioural – courtship differences
  • Mechanical – incompatible reproductive organs
  • Gamete – gametes not able to form zygote
22
Q

Explain postzygotic isolating mechanisms

A
  • Prevents hybrid offspring from reproducing
  • Zygote may be formed but hybrid zygote not able to undergo mitosis
  • Hybrid zygote may develop into sterile adult. Gamete formation prevented during meiosis
  • F2 fitness-offspring are fertile but F2 generation is sterile
23
Q

Explain the cenozioc era

A
  • This is the present era. Mammals diversified and human evolution commenced
  • Three periods: Palaeogene and Neogene and Quartenary
  • Mammalian diversification
  • Evolution of Primates
24
Q

Explain the paleozoic era

A
  • Era lasted 300 million years
  • All extant (living) taxa trace origins to Cambrium or earlier
  • Richness due to development of external skeletons eg. Trilobites
25
Q

Explain the precambrium

A
  • History of life is divided into Eras, Periods, Epochs
  • Oldest biological era is the Precambrium
  • Lasted 87% of geological time

4.5 BYA - formation of Earth
3.5 BYA – Oldest known fossils
2.5 BYA – O2 accumulates in atmosphere
2.0 BYA – Oldest eukaryote fossils
1.4 BYA – Protists evolve and diversify
600 MYA – Ediacarian animals
543 MYA – Cambrium animals

26
Q

Explain allopatric speciation fully

A
  • Speciation by geographic isolation
  • Something extrinsic to the organisms prevents two or more groups from mating with each other regularly, eventually causing that lineage to speciate.
  • Isolation might occur because of great distance or a physical barrier, such as a desert or river.
27
Q

Explain allopatric speication and gene flow

A
  • Can occur even if the barrier is a little “porous,” that is, even if a few individuals can cross the barrier to mate with members of the other group.
  • In order for a speciation even to be considered “allopatric,” gene flow between the soon-to-be species must be greatly reduced making mating impossible
28
Q

Explain parapatric speciation fully

A
  • No specific extrinsic barrier to gene flow.
  • The population is continuous, yet population does not mate randomly.
  • Individuals more likely to mate with geographic neighbours than with individuals in a different part of the population’s range.
  • Divergence may happen due to reduced gene flow within the population and varying selection pressures aross the population’s range.

eg ) The grass species Anthoxanthum odoratum

29
Q

Explain sympatric speciation

A
  • Large-scale geographic distance not required to reduce gene flow between parts of a population.
  • How? Ability to exploit a new niche may automatically reduce gene flow with individuals exploiting another niche.

Example, herbivorous insects try out a new host plant.

30
Q

Explain examples of sympatric speciation

A
  • Fish of lake Malawi – Fish in different parts of the lake evolved to become different species.
  • They end up occupying different parts of the lake and feed on different types of organisms.
  • Adaptive radiation through ecological release. Species evolve because of competition for food and resources
31
Q

Explain autoploidy and allopdoidy in plants

A
  • Autoploidy: small diploid seeded bananas produces diploid gametes because of nondisjunction. They would then produce a polyploidy which is sterile
  • Alloploidy: Reproduction between two species of plants to produce a sterile hybrid. Doubling of this chromosome number produce a fertile 3rd species, that can only breed with itself.
32
Q

Explain the factors influencing evolution

A
  • Continental drift
    The earth’s crust divided into tectonic plates that move because of seafloor spreading at ocean ridges
  • Mass extinctions
    Caused by climatic changes after meteoric events and/or after continents drift into new positions
  • Domestication
    Human induced selection of plants and animals (think of cattle, grains, dogs)
  • Vicariant events
    Are speciationeventswhere a species’ distribution becomes segmented and the separated populations evolve due to different selecting factors, causing the populations to become unique species
33
Q

Expalin examples of vicariant events

A
  • The present day continental masses of Australasia, Antarctica, Africa, Madagascar, India and South America were once a great, single continent that geologists call Gondwanaland or Gondwana.
  • Evidence of the Gondwanaland connection is still seen in some of the living flora and fauna of those land masses

Life Science 142 (16 decks)

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