Ecology Lab: An Introduction to Biodiversity
Sampling
Overview
Ecological communities are built on the interactions between the
organisms and the physical environment that surrounds them. The living
organisms, or biotic factors, interact as predators, prey and
competitors for resources. The physical environment, or abiotic factors,
such as water, sunlight, climate, temperature, soil and oxygen are part
of what determine how many living creatures can be supported in the
ecosystem. Plants are important in ecological communities. Not only do
plants represent a large source of primary production, they also
determine the potential for wildlife to exist in an area. Disturbance of
vegetation can have cascading effects through an ecosystem and changing
the diversity and abundance of plants will affect the other
living communities, such as animals, insects, fungi, and soil
microbes (Schulz et al 2009). In particular, the more sunlight and water
that is available in an area the greater the diversity of plants and
animals can live in that area. For example, picture the difference
between a desert and a tropical rainforest. The desert gets little water
so not very many plants can grow there, which leads to few animals
living there as well. In contrast, a tropical rainforest gets plenty of
both sunlight and rain and hosts a wide variety of both plants and
animals.
The question of how many species exists in an environment is central to
understanding why it is important to promote and preserve species
diversity. Promoting a singular species could leave an ecosystem at risk
of failure when environmental conditions change (AMNH
2015). Biodiversity is a measure of the number and variety of different
plant and animal species that live in an ecosystem. A high biodiversity
can be correlated with a more stable ecosystem because there are a wider
variety of resources for foraging, nesting, and seeking shelter. There
is redundancy in resources as organisms can meet their needs in a
variety of ways.
When studying an ecosystem, ecologists first try to survey what
populations of organisms naturally live there, then measure how many of
each organism lives there. This is referred to as the population
density of that species. Ecologists measure population density by
counting the number of each species in a sample area called a quadrat.
If they count the population size in a number of quadrats chosen at
random around the ecosystem, scientists can estimate how many of each
species live in the whole ecosystem. The carrying capacity is how many
individuals of a species that can survive in an area given the resources
(food, water, and nesting sites) available (Folgia 2008). Quadrat
sampling can either be random or systematic depending on the nature of
your research question. In random quadrat sampling, the habitat is
broken down into a grid-like system of squares and each square is
assigned a number. Then a random number generator is used to select
which square you will be observing. An example of
systematic quadrat sampling is transect sampling, which simply means
moving along a predetermined path, taking samples at predetermined
regular intervals, such as from the edge of the habitat into the center.
Sampling is done at regular distances to compare the biodiversity of the
edge of the habitat with the interior.
In this lab you will be performing quadrat sampling to gauge the
biodiversity of a habitat. You will get to choose where this habitat is
but remember that you MUST follow social distancing protocols while
completing this lab. If you can, complete this lab at your local park,
in your yard/courtyard, or in a green area that’s legally accessible. If
you can’t get outside, email me and we’ll figure out an alternative.
Be sure to read this whole lab before you head out so you know exactly
what is expected of you, and take photos of what you’re doing as you go
through this lab. You’ll be asked to attach your photos to the
conclusion before you submit this assignment.
Research question
How does plant diversity change when moving from to edge of the habitat
to the center?
Instructions
First, watch this video showing you how to conduct a quadrat sample:
https://www.youtube.com/watch?v=RhMOCxXcDrQ
Next, find something around your house that you can make a 1 meter x 1
meter square with. Here’s what I found at my house, but you could also
use rope, string, random branches, yardsticks, or whatever else you have
lying around. Feel free to get creative!