Ecology Flashcards
What is ecology?
The study of organisms in relation to their environment.
What are the 3 hierarchal levels of ecology?
- Organisms
- In their environments
- Conditions and resources
- Distribution and abundance
- Life histories
- Population growth and regulation
- Population dynamics
- Intra-specific competition - Species Interactions
- Interspecific competition
- Predation - Communities and ecosystems
- Nature of communities – patterns in space and time
- Flux of energy through ecosystems
- Flux of matter through ecosystems
- Food webs
- Patterns in species richness
Evolution by natural selection.
Organisms’ characteristics moulded by past environments
Variation in heritable traits contributes to fitness, better suited traits lead to higher fitness and more descendants – survival of the fittest
Selection towards fittest given available variation and constraints
Specialisation within species: ecotypes.
Fingerprint of natural selection, NS, can be seen within species
NS can favour different, locally specialised, variants where populations experience different environments and are relatively isolated
Ecotypes – genetically determined differences between populations that reflect local matches between organisms and their environment
Specialisation within species: genetic polymorphisms
Specialisation within species: genetic polymorphisms
Can also be distinct heritable trait differences within populations – due to heterozygotes of superior fitness (e.g heterozygosity to sickle cell anaemia being resistant to malaria), gradient of selective forces: differenced at end mixes in the middle, frequency dependent selection: e.g rare morph is not recognised by predators
Anthropogenic selection pressures
e.g peppered moths – industrial melanism, pollution from coal burning led to surface blackening and loss of moss and lichen, predators selected against light form on darker surfaces, darker in cities and to west of cities, went back to light once coal reduced, transient change
Speciation.
Species – a group of organisms usually with distinctive heritable traits held together by force of cohesion
Under the biological species concept, generation of viable offspring through sexual reproduction ensures genetic mixing and cohesion – maintain genetic gene pool
Turning off genetic mixing ‘tap’ can allow the evolution of new species – via allopatric and sympatric
Ecological speciation – from different selection regimes in subpopulations
Allopatric species – when secondary contact never occurs due to a geographical barrier
Sympatric speciation – subpopulations diverge despite no geographic separation
Continuous process, not a single event
Speciation on islands.
Islands provide a perfect setting for distinct species to form due to isolation
Adaptive radiation – rapid evolution of many species from a single ancestral species, often occurs on islands with many new ecological opportunities
Darwin’s finches – no other bird species when arrived to Galapagos Islands, adapted to eat many different things = variety of phenotypes adapted to different diets (ecological opportunities), niches filled by other species elsewhere
As islands are formed population become isolated and speciation occurs
Intersecting roles of geological forces, time, chance and evolutionary processes
Islands show us the historical element in match between species and environment, not just one perfect organism for each environment
Movement of land masses.
Islands provide a perfect setting for distinct species to form due to isolation
Adaptive radiation – rapid evolution of many species from a single ancestral species, often occurs on islands with many new ecological opportunities
Darwin’s finches – no other bird species when arrived to Galapagos Islands, adapted to eat many different things = variety of phenotypes adapted to different diets (ecological opportunities), niches filled by other species elsewhere
As islands are formed population become isolated and speciation occurs
Intersecting roles of geological forces, time, chance and evolutionary processes
Islands show us the historical element in match between species and environment, not just one perfect organism for each environment
Historical factors.
Species distributions adjust and readjust to past climate fluctuation
Distributions may not have reached equilibrium from last glacial period
Species now face much faster anthropogenic climate change beyond Pleistocene conditions
Caution in assuming a ‘match’ between species distributions and current conditions – hunting contrapted range of species
Convergent evolution.
Match between the characters of organisms and their environment can be seen in different groups solving similar environmental challenges in similar ways
Parallel evolution
When separate groups radiate in a similar way after they have become isolated
Despite evolving independently, two groups can be faced with similar challenges and opportunities resulting in similar forms, lifestyles and ecological rules
Illustrates how the process of evolution can result in similar (not identical) solutions given the same starting point and template of environmental opportunities
e.g placental vs marsupial animals
Biomes
Biomes – broad ecological zones characterised by communities of flora and fauna with characteristics broadly shaped by – and matching – their environments
Similar environments in different parts of the world leads to similar types of communities (biomes)
Classifying types of organisms
Biomes are characterised by the types of organism – not particular species
Broad classification systems attempt to group species by their characteristics regardless of taxonomic affiliations
Raunkier’s classification of plant life forms based on the position of the bud during cold or dry seasons – spectrum of his life forms varies across biomes, reflecting the match between life forms and environmental conditions, 1934
Biomes all consist of a variety of life forms, but the number of species of each varies with biome (and therefore prevailing conditions)
Diversity within communities
Great diversity within communities
Species can coexist by filling diverse ecological roles – herbivore, predator, decomposer
Coexistence of species constructed in a similar way (e.g same trophic level, taxonomically related) can be explained by – environmental heterogeneity (variation) in space and time, niche partitioning: similar species using resources and the environment in different ways
