3. 1. 2 - What is a species? Flashcards

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1
Q

why is the concept of species important for biologists?

A
  • can be used to measure biodiversity
  • by looking for changes in the species, the effect of natural environmental changes and changes as a result of human activity can be monitored
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2
Q

What is the morphological species concept?

A

a species definition based solely on the appearance of the organisms observed
- scientists would look closely at the inner and outer morphology of organisms to group them into species

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3
Q

state the negative of the morphological species concept.

A
  1. the appearance of an organism can be affected by many different things
  2. there can be a huge amount of variation within a group of closely related organisms
    - for example, organisms with sexual dimorphism, the different sexes could be grouped into a completely different species
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4
Q

define sexual dimorphism

A

when there is a great deal of difference between the appearance of the male and female of a species

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5
Q

what is the reproductive/ biological species concept?

A

grouping species based on the reproductive behaviour of the organism

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6
Q

what is the general definition of a species?

A

a group of organisms with similar characteristics that interbreed to produce fertile offspring

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7
Q

what are the strengths to this general definition of a species?

A
  • it overcomes issues such as sexual dimorphism

- is regarded as a good working definition for many animal species

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8
Q

what are the limitations to this general definition of a species?

A
  • populations of organisms of the same species may not interbreed simply because they are in different places, not because they are different species
  • if two species can produce fertile offspring then they can be considered the same species (e.g lion and tiger) even when they are not
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9
Q

what are the two definitions of a species that overcome the limitations of the general one?

A
  1. a group of organisms with similar characteristics that are all potentially capable of breeding to produce fertile offspring
  2. a group of organisms in which genes can flow between individuals
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10
Q

what are the positives and negatives of the reproductive/ biological species concept?

A

adv:
- good working model for most animals

disadv:
- much less helpful when classifying plants (which frequently interbreed with similar species to form fertile offspring)

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11
Q

what are the other definitions of a species?

A
  1. ecological species model
  2. mate-recognition species model
  3. genetic species model
  4. evolutionary species model
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12
Q

what is the ecological species model?

A
  • based on the ecological niche occupied by an organism

but niche definitions vary and many species may occupy more than one niche

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13
Q

what is the mate-recognition species model?

A
  • based on unique fertilisation systems, including mating behaviour
    (but some species may try and mate with other species - even produce fertile offspring - despite being different species)
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14
Q

what is the genetic species model?

A
  • based on DNA evidence
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15
Q

what is the evolutionary species model?

A
  • based on shared evolutionary relationships between species
  • members of species have a shared evolution and are evolving together
    (but not always easy to apply - there is not always a clear evolutionary pathway for a particular organism)
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16
Q

what does the term molecular phylogeny mean?

A

it is the analysis of the genetic material of organisms to establish their evolutionary relationships

17
Q

what are the limitations of all the species models?

A
  1. finding the evidence - many species haven’t been observed mating (setting up a breeding programme is time-consuming, expensive)
  2. plants of different species can still interbreed and produce fertile offspring, at what point should the offspring be considered a different species?
  3. many organisms don’t reproduce sexually. the definitions with reproduction are irrelevant for bacteria/ protoctists/ others that reproduce asexually.
  4. fossil organisms can’t reproduce + don’t have accessible DNA, but still need to be classified