Introduction to ecology Flashcards
what is ecology?
Scientific study of the distribution and abundance of organisms and the interactions that determine their distribution and abundance
Where do organisms occur?(distribution)
Why are the organisms there?(interactions)
How many individuals of each species are there?(abundance)
Why is ecology important?
Understand and manage threatened species/ecosystems
Direct threats (e.g. harvesting) and indirect threats (e.g. climate change)
Conserve and enhance ecosystem services
e.g. Food security, carbon sequestration
Improve human health
Understand host-parasite interactions and vector-borne diseases(e.g. mosquitoes -> malaria/Zika virus)
Main types of interaction
Interactions can be classified according to the effect of the interaction on the species involved: positive, negative, no effect
We can also classify interactions as trophic(involving feeding), or non-trophic
The effects of interactions
The effects of interactions between species are diverse and extensive they impact:
Population dynamics
Competitive exclusion
Community composition
Species distributions
Ecosystem function and properties
Evolution
Niches
In general, a species’ ecological niche can be considered as the role and position a species has in its environment, including abiotic and biotic factors. So, niches are a product of interactions.
Describing a niche
A niche is where a species does best in terms of temperature compared to precipitation pH etc. There is almost an infinite number of factors which makes estimating a niche very complex
A species may not be able to exist in an estimated niche area due to competition
Whereas in other species which are mutualistic they may only be extant where the other species persists. Realised niche is almost always smaller than fundamental (estimated) niche
(see diagrams in notes)
What is a population?
A group of interbreeding individuals found within a given area at a given time
But, what is an individual?- Obvious for many species
Unitary species: zygote, formed through sexual reproduction, grows into a genetically unique organism (e.g., us, fish, many insects)- a ‘genet
Modular species: Zygote develops into a module that asexually produces further similar modules- a ‘genet’ produces a ‘ramet’- This gives us two levels of individual (e.g., some plants, sponges, bryozoans, and corals)
Modular species example: Aspen
The largest organism in the world?
An Aspen grove in Utah covers 0.43 km^2. Each stem could be considered a ramet, and therefore an individual for the practical purpose of defining a population
Defining spatial distribution in mobile species
Spatial distribution used to define specific populations – difficult when a species is mobile e.g. migratory birds and more simple for sedentary species such as trees.
Populations may be defined as those able to breed together in an area
How do we describe a population?
local populations:
less frequent movement of individuals or reproduction (gene flow) between parts of a population can result in the definition of local populations within an overall population
Metapopulations:
populations throughout a landscape linked in this way through immigration and emigration are known as metapopulations
Reduced mixing between local populations results in patchy distribution
How do we define a population?
We can describe the number of individuals in a population, and their density (using area covered)
Density is useful for understanding population dynamics in the context of interactions, ecological processes and management
Density is more useful than abundance – is the population confined to a small area – in which case healthy or spread over a wide area where breeding may be an issue (for example)
How do we estimate population density?
Mark and recapture
GPS
Quadratting, line transects and belt transects
Point count (bird populations)
Population dynamics/ monitoring population change/population growth rate
see notes for equations
why are population dynamics important?
Many reasons e.g.- To manage and conserve species
- To understand birth and deathrates
- To estimate harvest rates – maximum possible whilst conserving the species or in the case of invasive species the minimum to remove to have a positive impact
Modelling populations: Exponential growth
e.g. Bacteria on a fresh agar plate or humans (since 1800’s)
R = per capita growth rate
T= time gone through
N = population at the start
(see notes for models and equations)
Max growth rate x population but taking into account k
K = maximum population aka carrying capacity of the environment
Above k population starts to decline ( death outweighs birth)
Growth is fastest at half of k
