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Year 2- Ecology > What is a species? > Flashcards

What is a species? Flashcards

1
Q

What is a species?

A

Doesn’t have one single definition = long standing problem

  • Concept is one of the oldest + most fundamental in biology but still no satisfactory definition- Dobzhansky (1935)
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2
Q

Why do species matter?

A
  • Underpins understanding of natural systems- hierarchy of life needs a definition
  • Biogeographical patterns forming across the world and how they form
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3
Q

Why does counting species matter?

A

mass extinction- by counting number of species we can determine what has been lost

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4
Q

Why is defining a species important?

A

Majority of species not well described

species inflation- elevated sub-species

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5
Q

What is species inflation caused by?

A

Political endemics- countries compete for highest number of endemic species
Conservation and careerism- new species in area make it more attractive + easier to get money

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6
Q

Name one of the 1st people to try and officially define a species

A

Ernst Mayr

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7
Q

Name the 5 different concepts used to define a species

A

Nominalistic
Morphological
Biological
Genetic
Phylogenetic

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8
Q

How may definitions of a species since Ernst Mayr are in use?

A

27 but keeps changing

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9
Q

Describe the contribution of Hey (2006) in defining a species

A

evaluated varying definitions and incorporated
various things e.g. morphology, genetics, sterile off-spring
Concluded that all species share the fact that they have arisen from evolutionary processes

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10
Q

What does this graph show?

A

Graph shows global primate species richness overtime- highlights species inflation:
- Increase in number of primate species is not due to discovery of new species but reflects changing ways people have tried to define a species
- These species were always there but were just defined differently

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11
Q

Describe an example of a new species being discovered

A

2017 = announced new species of orangutan- now 3 species instead of 2
Happened because they found a population of orangutans that were isolated and had slightly different characteristics e.g. denser fur, different teeth + genetically distinct from other 2 species
Scientists were aware they were there but the testing had never been done to be able to define them as a different species

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12
Q

As well as orangutans, describe another example of a new species being discovered

A

Genetic analyses of giraffes and found that there were 4 different species instead of 1 that was subdivided into 11
The reason this was done = conservationists wanted to ensure when relocating giraffes they wanted to maintain genetic diversity within species
Very distinct species which do not normally interbreed

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13
Q

Describe the nominalistic approach to defining a species

A

= philosophical view that only individuals exist in nature and species are artificial constructs of human minds
Species are entirely human constructs from basic human instincts- no biological relevance

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14
Q

What are the arguments for the nominalistic approach?

A

+ Different cultures vary in their classifications- able to understand different uses of species
+ Western taxonomy is not consistently seen
+ Number of types documented reflects interest or usefulness

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15
Q

What are the arguments against the nominalistic approach?

A
  • Differences among species often correlated- e.g. morphological, reproductive, genetic traits- evolutionary processes confused by this system as well as genetically inherited traits not linked with phenotype
  • Those traits reflect evolutionary past
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16
Q

Describe the morphological approach to defining a species

A

Things that look different are considered a species
Basis of traditional taxonomy (based on physical traits) but no theoretical foundation instead just looking at shapes of things and cross referencing it with a list of shapes of things identified by someone else in the past

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17
Q

What are the arguments for the morphological approach?

A

+ Physical traits map onto behaviour and evolution
+ Can be made quantitative e.g. MOBAT = morphology based alpha taxonomy
+ Type specimens used for comparisons

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18
Q

What are the arguments against the morphological approach?

A
  • Designations vary among taxonomists (lumpers vs splitters)- inconsistent taxonomic keys
  • Depends on feature selected
  • Omits reproduction, genetics and evolution
  • Excludes important non-visual characters (e.g. olfactory (smell), acoustic, behavioural)
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19
Q

Describe the biological approach to defining a species

A

groups of actually or potentially inbreeding natural populations that produce fertile offspring
Reproductively isolated from other groups
Requires detailed knowledge of each species

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20
Q

What are the arguments for the biological approach?

A

+ Reproductive isolation leads to genetic and morphological change
+ Many species cannot interbreed (or form sterile offspring)

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21
Q

What are the arguments against the biological approach?

A
  • Hybridisation common in many groups of animals- US Red wolf- speculated to be ancient hybridisation of grey wolf + coyote
  • Ring species = connected series of neighbouring populations that can interbreed but at the ends of the ring the populations don’t interbreed
  • Impossible to test effectively for all species- cant get all organisms to breed to test whether they produce fertile offspring
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22
Q

Describe the phylogenetic approach to defining a species

A

combines morphological approach with evolutionary history of an organism = populations differing by at least one taxonomic character (= particular attribute of an organism)
Common ancestry (no hybrids), aka monophyly- all descendants have one common ancestor
Ignores reproductive isolation but differ in some aspect of their morphology = different species

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23
Q

What are the arguments for the phylogenetic approach?

A

+ Reflects evolutionary history
+ Identifies divergent populations = accumulation of differences between closely related populations within a species

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24
Q

What are the arguments against the phylogenetic approach?

A
  • Often increases number of species by 50% = species inflation
  • May be picking up trivial differences- no adaptive significance e.g. different dog breeds
  • Driver of species inflation: many controversial species
  • Usually elevates existing sub-species or populations rather than discovering entirely new organisms
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25
Q

Describe the genetic approach to defining a species

A

uses DNA analysis techniques to separate species with no other info required- useful as statistical analysis and data processing techniques can be used to reduce subjectivity
Do not need to know anything morphological about sample being tested
Increasingly rapid due to PCA = principle component analysis

26
Q

What are the arguments for the genetic approach?

A

+ Bar-coding allows ID by non-specialists
+ Works well for sympatric groups- ones that exist in the same location
+ Identifies cryptic species = species that look the same but are genetically distinct
+ Valuable for group with no obvious visual differences e.g. fungi, mosquitoes

27
Q

What are the arguments against the genetic approach?

A
  • No fixed boundary between species is possible
  • Consistent rules are not applied
  • Genetic exchange does occur among species = obscures boundaries
  • Works poorly for allopatric groups- ones that exist in different locations due to genetic drift = change in gene pool of a small population due to random chance
28
Q

If a species cannot be defined, what is it?

A

Hypotheses- moving targets that have to be frequently updated as new tools are improved or invented

29
Q

What is an ESU?

A

= evolutionary significant units = populations of organisms that could be defined as the same species but are distinct for purposes of conservation

30
Q

What does biodiversity + species richness correlate with?

A
  • Higher taxonomic levels
  • Traits and characters
  • Functional diversity
31
Q

What does species richness and biodiversity not reflect?

A
  • Genetic diversity
  • Phylogenetic diversity- could be more useful than species richness
  • Representative plant species
32
Q

Describe Linneas’ nomenclature system

A

= system of naming organisms by 2 words = species + genus

33
Q

How many species did Linneas identify?

A

9000- mostly temperate with a biased composition- we know now this is not correct

34
Q

Describe some more recent attempts to classify species

A

Stork (1993)- estimated 1.8 million species with expert assessments and a compilation of sources

Catalogue of life = 92% coverage of taxa- 2018 = 1,754,878 species
- 61,579 extinct
- 84% undescribed
- 14th September 2023= 2,119,462 species

35
Q

Name 4 ways to estimate number of species

A
  • extrapolation of data
  • Scaling body sizes
  • Scaling taxonomy
  • sample based estimates
36
Q

What does this paper show about discovery rates?

A

Projections were modelled of species estimates based on current rates of discovery of different groups

Some groups of organisms are better described than others- discovery rate in birds and mammals flattens whereas other groups have a greater trajectory – so more species to define

37
Q

How many species are estimated after extrapolation of data?

A

6-7 mil

38
Q

Describe some problems with extrapolating data when estimating number of species

A
  • Assumes similar patterns
  • Poor when few known
  • Inconsistent species concepts post 1984
  • Tropics under sampled
  • Incorrect taxonomy
  • PCR (=polymerase chain reaction) allows DNA sequencing- discovery rates increased after PCR was invented which causes disruption when extrapolating data
39
Q

Describe an example of extrapolation of data

A

e.g. Raven-1985- looked at difference in species richness in tropics vs temperate regions

RESULTS:
- 2:1 tropics: temperate- more known about species here as western scientists live here
- 2/3 described insects are temperate
- 3-5mil total insects after extrapolation

40
Q

Are species names valid?

A

US fossil mammals- many of these were named wrong
- Well studied group
- Not species rich
- Many synonyms = misnamed taxa

But- lag in revision as there are many new species and studies show it is only revised every 10-100 years

41
Q

Name another way to estimate number of species

A

Scaling- body sizes

42
Q

Descibe the method of scaling body sizes

A

sort of method of extrapolation but biological characteristic is used that is common to certain groups to predict changes in numbers

43
Q

What is this graph showing (May 1988)?

A

approximately linear relationship between body size and number of species
= smaller the body size the more species there are = negative relationship

44
Q

Evaluate the use of scaling body sizes to estimate number of species

A
  • More small species
  • 10 x length = 10³ volume of organism – 100 x species
  • Breaks down below 1cm- When very small body size (below 1cm) the relationship breaks down
  • Very vague method
  • Assume only true to 0.2cm
45
Q

How many species are there estimated to be when following the scaling body sizes method?

A

10mil species globally

46
Q

What is another thing that can be scaled to estimate number of species?

A

Taxonomy

47
Q

Describe what these graphs are showing

A

e.g. Phylum levels off (at the asymptote) showing all phyla have been discovered- makes sense as broad category
e.g. species level is nowhere near the asymptote = shows have not discovered them all
7th graph- combined all patterns which shows if move up taxonomic level = clear relationship between number of species expected at each level

48
Q

What is an asymtote?

A

When line levels off on a graph = maximum capacity

49
Q

How many species were estimated when scaling taxonomy?

A

8.7 billion

50
Q

Describe the method used in this paper

A

12 year old paper that is highly regarded = another form of scaling using taxonomy:
Looked at number of taxa known at each taxonomic rank e.g. genera, class etc- estimated an asymptote = when line levels off

51
Q

Describe an example of sample based estimates

A

Erwin (1982) in Panama =
Wanted to estimate number of TRF insects:
1. Used intensive campaign of sampling in rainforest using Canopy fogging
2. tents are put below trees to catch the dead stuff

RESULTS = Fogged 19 trees and found more that 1100 species

52
Q

Define: Canopy fogging

A

= process of applying insecticide to foliage of trees and shrubs

53
Q

What is the Coleopterists bulletin?

A

refereed quarterly journal which includes a wide variety of articles on taxonomy and ecology of beetles (= Coleoptera)

54
Q

What was done with Erwins findings and what were the results?

A

Data was extrapolated:
RESULTS =
- 40% arthropods are beetles
- There is 2 x the species richness in the canopy vs floor
- 50,000 species of Tropical trees can calculate and come to estimate that there are- 30mil tropical rainforest arthropods, 100mil species globally

55
Q

What is a cryptic species?

A

biological groups that look identical but cannot interbreed

56
Q

Describe a study on cryptic species

A

Hebert et al (2004):
= 10 caterpillars that are all different species- however the adult emerging from caterpillars looks exactly the same
- Scientists believed they were different morphs of same species
- Discovered to be a cryptic species after genetic analysis and studies on host plants

57
Q

What are estimates based on and why is this?

A

animals as most common and similar to humans = more likely to study

  • > 70% named species = animals
58
Q

How many bacteria are estimated to have been named and why is this?

A

5% of bacteria- bacteria evolve so rapidly that estimate is most likely out of date

59
Q

How many plants are said to have been named?

A

400,000

60
Q

Describe what the method of this study

A

Best estimate
Method = give overview of different ways people estimate species richness- shows how varied these methods could be
- Leave out certain groups to highlight how varied methods can be e.g. bacteria included value of species richness = 1 trillion

Year 2- Ecology (7 decks)

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