Classifying Environments Flashcards
John ray
1686
First attempt at a definition of a species
Based on how they look and they stay the same - fixed
Carl Linnaeus
1735
Idea of taxonomical hierarchy based on shared physical characteristics
Ernst Mayr
1942
Organisms within a species can reproduce with one another
And they cannot reproduce with organisms of other species
Why and how do DNA sequences change over time
- Replicating organisms and the DNA in them increase in numbers exponentially
- there are not enough resources or space in any environment to support unlimited population growth. At some point there will be competition for these resources – a ‘struggle for existence’.
- Random mutations
What is a species - Ernst mayr
A group of organisms that can interbreed and produce fertile offspring
Problems with Ernst Mayr ‘s definition of a species
Hybrids- sub-species
Quite animal centric
Does not explain how species originate
Bacteria - most abundant and diverse organisms on the planet do not interbreed
George Simpson
1951
Members of a species share an evolutionary process
Adaptive evolution
Selection will cause a permanent change in the composition of the population
Adaptive trade-offs
Traits that evolve and are adapted to one environmental condition mean the organism is less adapted to others…
Operational taxonomic units
Practically a % DNA similarity level is used ~98% to collect samples into the same ‘species’
To avoid misrepresentation – these collections of samples with DNA >98% similarity are called
Operational taxonomic units (OTUs) or molecular operational taxonomic units mOTUs
Or phylotypes = a biological type that classifies organisms based on their genetic characteristics and evolutionary relationships
Environmental metabarcoding
Ancient ecosystems
Plant-pollinator interactions
Diet analysis
Invasive species detection
Pollution response
Air quality monitoring
Neutral ecology
Different species are functionally equivalent
Different due to chance
Chance processes that change evolution
Bottleneck effect
Founder effect
Niche
A concept of an organism’s environmental tolerances and resource requirements
Eg temperature, pH, pollution, prey, nest locations
Multi-dimensional
Resource vs conditions
Conditions are NOT competed for eg temperature
Resources are competed for eg space , food
Measuring fitness in a particular niche
Ability to leave viable offspring
Fundamental niche
The environmental parameters across which an organism can survive
Realised niche
The environmental parameters across which an organism can reproduce
What do ecologists use to define niches
Ordination analyses - collapse multiple dimensions into 2 main ones that show the main environmental patterns
Ecosystem engineer
Any species that creates, significantly modifies, maintains or destroys a habitat
Allogenic engineers
Change a physical part of the environment
Autogenic engineers
Creates habitats biologically eg coral
Crepuscular
Only active dawn or dusk
Cathemeral
Active all times of the day
Diurnal
Active during the say
Nocturnal
Active at night
Niche construction
Trait must be heritable and correlated with reproductive success
The Crabtree effect
Yeast- kills the competition and creates a new niche dimension (high ethanol concentration) when anaerobically respires
Population
A group of the same species in the same place at the same time
Population change
A function of birth and death rate
Numbers now
Numbers before + proportional change of [numbers before] + [Immigration – Emigration]
Carrying capacity
defines the maximum number of individuals it will support… think limited space or resources
Number now (carrying capacity)
Numb before + Numb before x proportional change x f [carrying capacity]
What is used to estimate birth and death rates
Life tables
Speciation
If populations remain disconnected for sufficient time, then either adaptation to different niches and/or neutral processes may/will lead to differential evolutionary trajectories …
At some point these populations are unable to interbreed and/or they become genetically divergent
… this leads to the two populations being sufficiently distinct to be classed as different species since they have sufficiently different evolutionary histories
Life history tables
For each ‘cohort’ each generation/time
Number born
Number survive
Number offspring
Calculate these and make proportions etc to derive birth and death rates
This can allow an estimate of the basic reproductive rate of the population
Classification of survivorship curves
type 1: mortality concentrated toward the end of the maximum life span (humans, pets)
type 2: constant mortality rate from birth to maximum age
type 3 : extensive early mortality, but a high rate of subsequent survival – typically many offspring produced (most common in nature)
