Biology Labs Page 2
LAB - ON BEING A FIELD NATURALIST: ORGANISMAL MICROENVIRONMENTS
The essence of individual ecology is in studying and disentangling the
constraints and limitations imposed on an organism from its environment.
But, in fact the "environment" of an organism is actually a composite of
several different environmental types, each representing a distinct set of
problems the organism must "solve" simultaneously in order to survive and
reproduce. To illustrate:
phylogeny/history biophysical environment
genetics (light, temperature
\ / humidity, wind, etc.)
/ . \
predation/parasitism . resource environment
The organism must find food, water and other resources from its
"resource environment," but it only has a limited set of means to find,
catch, and eat its food (e. g., its eyes, hands or other appendages, and
mouthparts). Additionally, it must digest that food, and not all food is
equally digestible. Thus, a particular food item to one critter may be
entirely inedible (perhaps even dangerous) to another critter.
The organism must also secure mates, and that could mean establishing
a territory, engaging in lengthy courtships with potential mates. Its
success at these depends on how many and how big are the other mating
competitors and mating prospects out there and that's called the
The organism must also avoid being eaten and avoid too much of a
parasite load. Organisms typically possess elaborate means either to avoid
detection, evade capture, or hamper digestion by a predator (e. g., by
being toxic). Some organisms can do all of these at once. Note that which
tactic to avoid predators/parasites will depend very much on the specific
attributes of the predators/parasites out these and that's called the
The next environmental type "phylogeny/history and genetics" isn't
really an environment at all, but is meant to represent that an organism
has an evolutionary ancestry and genetic background - neither of which can
be known by observational means alone. For example, you can never look at
any particular trait and state with certainty that it evolved because it
conferred greater survival and reproduction. In fact, the trait may make
no difference at all. The point is that an organism's genetics and the
history of its life up to the present instant greatly determine the range
of actions, or phenotypic response, it can take when faced with the next
ecological problem (e. g., a predator) or in an evolutionarily novel
situation (e. g., global climatic warming, ozone depletion, etc.).
Finally, the last environmental type reflects the organism's
requirement that it maintain physiological homeostasis in order to perform
all of the functions necessary to do everything else. Success at life
necessitates that an organism must avoid microclimates that exceed its
typically narrow physiological tolerance limits, and instead select
appropriate places to live which do not impose physical stress out of the
range of those available in its "biophysical environment." This is because
biochemical compounds that govern life processes (e. g., metabolism,
synthesis, and structure) are all affected by body temperature.
Many organisms maintain control over their life processes by
regulating their temperature. For mobile animals this may involve
selection of favorable microclimates out of the range of those available in
their environment. Other mobile animals, such as birds and mammals, are
buffered to some extent against environmental variation by generating body
heat internally (endotherms) and possessing an insulating layer (feathers,
fat and/or fur). But for sessile (immobile) animals and plants, fewer
options are available, and microclimate selection must occur during seed
dispersal, or by producing enough progeny to insure that at least some
reach locations suitable for life.
Relative to you, organisms have different sizes, shapes, colors,
metabolism, insulation, and abilities to move; thus, they are living in a
totally different world than you are. Small flecks of sunlight in a forest
from your point of view become huge sunny clearings to mushrooms,
understory plants and insects. To the tiniest of cretons, that often
number in the millions in a single field, a seemingly monotonous lawn
becomes a treacherous matrix of brambles and exhibits huge temperature and
moisture gradients from soil level to the tips of grasses only a few
centimeters up. These small cretons are also constantly at great peril
from the threat of predation from ever-present predators yet not much
bigger than a pea. What a life!
In this lab, you will try to put yourself in the world of other life
forms, observe the problems their environments impose upon their lives, and
try to comprehend how they go about solving them. An understanding of
organism*microenvironmental interactions is pivotal to understanding
environmental sources of selection and how they act to create and maintain
the diversity of life forms in our world.
Methods for Today's Lab.
Today, following a brief discussion about the physical and biological
processes that determine the interaction of organisms and their
environments, we will GO OUT INTO NATURE and put these new skills to work.
We will travel to a local park (Taylor Arboretum), and conduct pairs of
timed "focal" observations during 10 mins of QUIET SOLITARY OBSERVATION.
First "focal" pair: Habitat Comparison. Find two totally different habitat
types and sit in each for a 10 minute focal period. This is actually
a fairly diverse park. There is a pond, a meadow, a creek, a wooded
slope, forest "edges", and human artifacts to avoid (footpaths, the
environmental education center, and driveway). Record what you see,
hear, smell, touch, etc., and of any and all life forms encountered.
Include descriptions of the plants around you, above and below, and
the consequences of ambient or "operative" microclimates to any plant
life in your vicinity and to any animals that happen by. If any
visitors are small enough, catch one in your sample bag to make
Second "focal" pair: Organism Comparison. Find two different types of
organism but that are somewhat similar taxonomically (e.g. two
species of understory plants, two species of arthropods, two species
of vertebrates). Conduct a 10 minute "focal" on each of them noting
their similarities and differences and speculate on how each may be
"designed" differently given their divergent lifestyles and tasks you
witness them performing. Exactly where are each found? Why might
each be where you see them? What are they doing and why? How are
characters of each's surface (size, shape, color, type of skin, etc.)
relevant to each's physical microclimatic requirements? How are
each's characters relevant to foraging, social interactions, or
Some Extra Comments.
While you are writing, clearly indicate what is observation and what
is interpretation. The difference between these two processes is
fundamental to your development as a scientist. Remember that almost every
observation has at least two or three alternate hypotheses to explain it
stemming from different requirements according to the different types of
environments listed above. See how many "totally different" hypotheses you
can formulate to explain the same observation.
If hand lenses are available, take one along with you for observing
small details of plants and animals. Also, take along a sample jar for
detaining small arthropods (release when noted). I will help you to
identify organisms you encounter, but don't let not knowing the name of
something stop you from describing and attempting to explain what it is
doing, or not doing. If thermometers are available, record a few substrate
temperatures in the sun and shade, and at and slightly below ground level.
Note the HUGE differences in temperature over very small distances.
Toward the end of the period, we will return to the lab and compare
observations and interpretations of the natural history we collected. You
will not need any books. Do not bring portable music players. Also,
please do not use any insect repellant, tanning lotion, or smoke because
the scents of these products will affect the outcome of your efforts.
some comments to lab instructors:
(1) Crank through the five environmental types figure using a real example
(e.g. a lizard)
lizards regulate TB by finding warm sunny places to sit
lizards regulate water by eating wet food and drinking
lizards typically eat bugs (but some eat plants)
lizards have to be the right temperature in order to digest their food
most lizards are both polygynous and polyandrous (multiple matings among
numerous individuals of both sexes), but within a breeding season,
they're typically just polygynous. Lizards are typically highly
territorial, with the larger lizard typically winning a typical
social interaction, and that's one way they carve up space.
lizards are eaten by other lizards, snakes, birds, and even some large
arthropods like centipedes. Occasionally they are even killed by
carnivorous plants (but this was only reported for the dumbest extant
lizards are often heavily parasitized internally by malaria, lung and liver
flukes and intestinal parasites. Also, ectoparasites include
mosquitos (which also bring them malaria) mites and ticks (and there
is some hot new data suggesting that lizards may be carriers of Lyme
lizards have a fairly well-known evolutionary history. One of the striking
features is that of local environmental adaptation, especially in the
things that many physiologists would prefer to believe do not change
(e.g. body temperature, locomotion, and digestive performance).
an hypothetical example of an observation with many different hypotheses
could be - why did the lizard go over and sit in a place illuminated
(2) Stress that they should write complete sentences using GOOD ENGLISH.
Upon return to the classroom have each person actually read out loud
from their field notes.
(3) Think about winter questions -
why is the canopy deciduous but the understory green?
what do organisms do about freezing?
(4) Above all, I really suggest that YOU do the exercises as well along
with your students. After you set them up, get out your notebook and
write down stuff. This will set a good example and at the same time
will give you ideas about what they might be seeing and what they
might talk about upon return to the classroom.
(5) Tell them to go away from the path, road, etc., and not bother to write
down sounds of airplanes, cars or other nonsense.