Download Unit Three - Montana State University Extended University

1
Astrobiology Short Course
Unit 3a: Energy In The Environment
In this unit, we'll be talking about the "environment" a lot. Most people think about trees, rocks,
streams, and "nature" when they hear this word. But really, your "environment" is anything
around you that isn't you! We could talk about your "classroom environment" or your "home
environment" or we could go very broad and talk about our planet's "stellar environment." Your
environment goes out in layers, from immediate to local to regional to global. We all "care about
the environment" but we usually care most about what's closest to us!
We'll also be talking about energy, and that's a lot more difficult to define. It's often called "the
ability to do work" but that’s only useful if you understand exactly what "work" is...and that's
about as hard to understand as energy! Let's think about energy in a very rough sense as the
ability to create change. Growth, changes in movement, generating light, sound, or heat — all
these are evidence of energy at work. Every living organism uses energy from its environment to
move, live, grow, and reproduce. An environment without energy would be cold, dead, and dark,
rather like interstellar space (though even there we find traces of energy).
We're most often told in our textbooks that "all our energy comes from the Sun," but that's not
exactly true. Yes, the Sun provides us with tremendous energy, but there's also plenty locked
inside the crust of our planet: some radiating from the molten core, some trapped in rocks and
released by radioactive decay, and some stored in chemical bonds within the earth.
Energy is the same no matter where it comes from. You might think that movement, electricity,
and light are very different kinds of energy, but the truth is, you can always change one to
another. Energy can change form: light energy from the Sun changes to heat (vibration) energy
in water, then motion energy, lifting water to the atmosphere and falling as rain, then driving a
turbine as water spills over a dam and turning into electrical energy. The electricity can be used
to break chemical bonds, separating water into hydrogen and oxygen, and the chemical energy
released by re-forming those bonds can drive a hydrogen car! Energy is continually "dancing"
through its different forms in nature.
Energy is essential for life. No energy, no life. Why? Because life is all about change, and
energy is needed to create change. We once thought that sunlight was necessary for life, but our
extremophiles discoveries changed our thinking; it is now obvious that chemical or geothermal
energy can be used for life processes instead of sunlight.
Sidebar: Additional Resources
US Department of Energy website for kids featuring games and activities, energy calculators,
and information for teachers http://www.eia.doe.gov/kids/energy.cfm
2
California Energy Commission offers a kid-friendly discussion of energy, movies, and teacher
resources http://www.energyquest.ca.gov/story/chapter01.html
Elementary school information handouts describing energy
http://www.need.org/needpdf/infobook_activities/ElemInfo/IntroE.pdf
Unit 3a: Gathering Energy
Energy is gathered chemically by living organisms. What does that mean? Energy can be stored
in chemical bonds to be released later. It's a bit like stretching a rubber band or compressing a
spring, except that it's done at an atomic level. For example, carbon dioxide (CO2) is a very
stable, "low-energy" molecule, rather like a "relaxed" spring. Glucose, on the other hand (a
simple sugar, C6H12O6), is a more "unstable" molecule, a "compressed" spring ready to break
apart and release energy. So if a living thing were able to take CO2, along with some water, and
squeeze it together into C6H12O6, it would be storing energy, right? That's exactly what plants
do, and it's called photosynthesis. That energy has to come from somewhere, and plants use
light, or radiant, energy to do the "squeezing."
Not every organism can is capable of storing energy using photosynthesis. Plants have
specialized cell machinery (chloroplasts) that manufacture sugar using sunlight. Certain types of
archaea and bacteria, such as those living around deep-sea thermal vents, instead harvest energy
from sulfur and iron compounds in a process called chemosynthesis. Regardless of the source,
any organism that can harvest energy directly from the non-living environment is called an
autotroph, a word that means "self feeding" (autos=self, troph=nutrition). The first forms of life
on our planet must have been autotrophs. Were they photoautotrophs harvesting sunlight, or
chemoautotrophs relying on chemicals? Scientists are divided on this issue, though more seem
to be favoring the chemoautotrophs hypothesis, mainly because that type of metabolism doesn't
require oxygen, and we know that free oxygen was very scarce in the early stages of life on our
planet.
This leaves a very large class of organisms, including you and me, who can't do either type of
synthesis and therefore can't feed directly off the non-living environment! We need that stored
chemical energy, but can't make our own — so we conveniently obtain it by consuming the
autotrophs. That may seem a little rude, but evolutionary theory makes it inevitable: if there's any
convenient source of energy, some life forms will find a way to use it. This is the strategy of the
heterotrophs (heteros=different, troph=nutrition) — eating other organisms to obtain energy.
All animals are heterotrophs, along with some single-celled creatures. Oh, and by the way, the
heterotrophs aren't safe from being eaten, either, since they have tasty stored energy as well! In
fact, anything that makes complex organic molecules (like sugars) might as well have "food"
written on it.
Sidebar: Word Soup
3
Science sure has a lot of vocabulary! It can be bewildering to deal with terms like
photoautotroph and chemosynthesis while trying to learn the basic concepts of "who eats what."
One trick that's helpful is to remember that these long words are just strings of prefixes, bases,
and suffixes, often from Latin or Greek, with well-known simple meanings. We can
"reconstruct" the meanings by putting the parts together. Here are some of the word parts we're
using in this unit:
Prefix
Meaning
Base/Suffix
Meaning
PhotoChemoAutoHeteroExtremoMeso-
Light
Chemical
Self
Other/different
Extremes
Middle
-troph
-synthesis
-phile
-phobe
Feeds
Building
Loves
Fears/hates
So, the word "photoautotroph" just means "Light-self-feeds" - it feeds itself using light! What
would be the meaning of "chemosynthesis?" How about "mesophile?" Knowing and
understanding the meanings of common scientific prefixes, roots, and suffixes is critical to being
able to comprehend science writing, because even complicated and unfamiliar terms can often be
deciphered ('de-'=undone, 'cipher'=code) this way!
Here's one web resource with a comprehensive list of these "building blocks" -- you might
consider a more subject-focused list as a handout or reference when learning science vocabulary.
Unit 3a: A Web of Energy
We can think of energy as "flowing" through lifeforms, starting with the autotrophs (also called
producers) and then moving to the heterotrophs (also called consumers), and then maybe to other
consumers, and so on. This is typically called a food chain or more accurately, a food web. Food webs
are really interesting to study, because they show the intricate dependence that organisms have on each
other. A typical food web has autotrophs (producers) on the bottom, with arrows showing how their
energy flows to the heterotrophs (consumers) that eat them, then to higher level consumers, all the way up
to the top, where we find creatures like lions, eagles, killer whales, and of course, human beings. Though
we're not immune to being eaten, people are considered "top predators" — consumers that aren't normally
food for other predators.
Sidebar: Land and Ocean Food Webs
Here are two examples of food webs, one with land creatures, one in the ocean. Both are
"incomplete" -- food webs in nature are very, very complex -- but both show interesting
information. Notice the direction of the arrows, from the "food" to the "eater." Students often
4
have a hard time remembering this. Just have them notice "the arrow is like food going into a
mouth."
In fact, what the arrows represent is a flow of energy.
Notice the arrow going back downward towards the
decomposers like fungi and bacteria? Even top predators
end up being "food" for something!
In order for students to understand food webs, they should
build them, preferably from verbal descriptions. Even after
being told repeatedly, many students will get the arrow
directions wrong. Reinforce repeatedly, the arrow
represents the direction of energy flow.
Notice also how food webs can reveal important
dependencies among creatures. In the ocean food web, the
widespread destruction of zooplankton would be a disaster
for nearly all sea life. The elimination of squid, however,
would have a lesser impact -- both the shark and marlin
have alternate food sources.
5
Unit 3a: There's Less at the Top
There's another very important factor in understanding how energy flows through living systems.
As energy moves "up" the food web, there's a lot less of it available. In fact, every time we move
up one "eating level" (called a trophic level) we typically lose about 90% of the energy! Where
does it go, since energy can't be destroyed? Remember that animals (and even plants) have to use
energy to move, grow, and reproduce. Plus, we can never extract 100% of the energy of an
organism by eating it. Most of the energy is "used up" and turned into heat and motion before the
organism gets eaten, and the predator gets only a small amount of what's left.
Finally, we should point out that there are strategies other than simple kill-and-eat (predation)
that can work to get food for a heterotroph. We've talked a little about decomposers, organisms
like bacteria and mushrooms that slowly "digest" the dead tissues of plants and animals.
Scavengers like buzzards and hyenas are also perfectly happy to wait until their meal's no longer
6
moving — less chasing and fewer teeth and claws needed! Finally, we have parasites. Living
inside, attached to, or near their host organisms, they take energy away from the host like a
predator, but very slowly...in many cases not killing the host at all. Evolution says that any
strategy that can work will eventually be tried — and if it's successful, it will become common.
This means that top predators (like us!) need a whole lot of lower level consumers and producers
available to support our meat-rich lifestyles. Vegetarians need a lot less, because they eat the
producers directly. In a food crisis, we might expect to become much more dependent on grains
and vegetables for our food. Luckily, human beings are omnivores, able to eat just about
anything! A true carnivore "top predator" such as a lion can eat only meat, and requires a large
population of herbivores like gazelle and wildebeest to survive. If we did a rough measurement
of total "living mass" (biomass) for grass, herbivores, and lions, we'd likely find that it takes
10,000kg of grass to feed 1,000kg of herbivores to feed 100kg of lion. (You could substitute
"pounds" for kg and it would still be true). Sometimes we show this model as a "pyramid" called
a food pyramid or an energy pyramid.
Sidebar: An Energy
Pyramid
Pictured here is a simple "energy
pyramid" for an ocean ecosystem.
Notice that only one "top predator"
is shown at the apex, which is
typical.
Notice also that it takes about 1000
times the fish's mass in
phytoplankton to support this one
fish through its life!
Sidebar: Unusual Strategies
We're no doubt familiar with such "common" parasites as tapeworms, fleas, ticks, and mites. Our
pets are all too familiar with them!
But parasitism is such a common strategy that some parasites become "specialists" relying on a
single host species.
One of the world's most unusual parasites is Cymothoa exigua, the "fish tongue eater" parasite.
Its larva bores through the gills of its host, the red snapper fish, attaches itself at the base of the
tongue, and begins living off the rich blood supply there.
7
Over time, the snapper's actual tongue atrophies and dies, and the parasite actually becomes the
fish's new tongue. The snapper continues life normally, able to use its new tongue just like the
one it was born with -- except it's now sharing its food with the parasite.
Want more details? See if you can stomach them!
Activity: Modeling an Alien Food Web
We don't necessarily know what life-forms and ecosystems we'll find on distant worlds, but we
do know this: They all require energy. Anywhere there's life, some form of life must be
extracting energy directly from the surrounding environment (an autotroph). While there don't
necessarily have to be heterotrophs, or consumers, biologists would be surprised not to see
something taking advantage of a ready food source. So while the lifeforms may look totally
unfamiliar, we should be able to classify them according to their food sources as autotrophs or
heterotrophs, and determine some type of food web. Let's just hope we don't become part of
that food web!
Dr. Emily Xeno, famous astrobiologist and xenobiologist (a scientist studying alien life-forms)
has just returned from an expedition to Rigel-6, which turns out to have a thriving ecosystem.
Below is a synopsis of her diary. See if you can fill in a basic food web of the creatures she
discovered.
Using the diary for clues, drag each creature's name onto the food web below. There is only one
right answer, and each name will only snap into its proper place on the food web. Remember the
arrows go from food source to "eater."
8
Unit 3a: Assessment
1. An organism that can gather energy directly from its (non-living) environment is:
a heterotroph
a parasite
an autotroph
9
a consumer
2. The purpose of both photosynthesis and chemosynthesis is to:
create pigments in plants
create nutrition for animals
use sunlight or chemical energy to build complex molecules
break down complex molecules using sunlight or chemicals
3. A food web shows what useful information?
the amount of energy transferred from prey to predator
the populations of one organism relative to another
the nutritional needs of an organism
which creatures depend on which other creatures for food
4. Which of the following show four strategies for a heterotroph to obtain energy?
predation, parasitism, scavenging, decomposing
photosynthesis, chemosynthesis, biosynthesis, recombination
predation, consuming, producing, decaying
harvesting, synthesizing, decomposing, respiring
5. Energy can be loosely defined as the ability to create:
change
motion
randomness
life
Unit 3b: Living and Non-living Environment
Imagine yourself fishing on the banks of a lovely stream. It's a sunny day, the fish are biting, and
unfortunately, so are the mosquitoes. You're sitting on a large, comfortable rock with a soda and
some chips. You're pretty much at peace with your environment here, but the scientist in you
says, "Maybe I should figure out how to classify my environment." (Sometimes scientists have
trouble just enjoying the moment!)
10
We've talked a lot about how to classify living things, but what about all the stuff in your
environment that isn't alive? What about the rock you're sitting on, the sunlight shining on you,
the water, your snack, and your fishing pole? I guess our first step is to sort out the living
environment, which we call biotic factors, from the nonliving environment, which we call
abiotic (not biotic) factors. That should be pretty easy: fish, grass, me, those darn mosquitoes, all
go in biotic; rock, sunlight, water, fishing pole are abiotic, my snack...hmm.
I'll call that soda abiotic, but those chips were once potatoes, and they were living...what do we
call a dead thing, abiotic or biotic? That's sort of in a "gray area." We'd certainly call a living
cow biotic; the minute it dies, is it abiotic? If we were a buzzard or other scavenger, would we
make the same decision? Since "recently living" things are important food sources, just like
living things, scientists normally classify them as biotic. If it comes from the living world, it's
biotic. Now, once the bacteria and fungi have completely broken down that dead tree or cow into
soil, and it's no longer an important food source, we can consider it part of the abiotic world.
Sidebar: Additional Resources
Utah Education Network lesson plan on teaching abiotic and biotic factors
Utah lesson plan on understanding characteristics of living things
A lesson plan with a short reading selection, a classification activity, and a scavenger hunt,
introduces learners to the classification of natural materials and ecosystems
Unit 3b: Resources in the Biotic World
Okay, we've got our first level of sorting-out done! Now let's tackle the biotic, or living world,
things. I can certainly classify them into their fancy genus and species names, but let's look from
a more practical viewpoint — how are those living things important to me? I might want to
classify living things into three groups:
Things that I can eat (here, fishy!)
Things that can eat me (*swat* Dang mosquito!)
Things that cooperate with me (hey, Rover! Good boy!)
I might want to add a fourth category as well. That black bear just upstream from me is catching
all my fish! I don't think the bear will eat me (though it might think my little dog is tasty), but it's
certainly competing with me for my meal, and that's important to me. So let's add one more
bullet:
Things that compete with me for food or resources.
Now, if I were to imagine myself as a fish, or an insect, or even a mosquito, could I still classify
all living things into these four categories? Would I classify them differently? Try an exercise in
11
"points of view" by classifying different biotic things as food source, predator, friend, or
competitor. (We'll stretch the use of the word predator to mean "anything that eats me" even if
it's just a bloodsucker — normally predator means anything that kills and eats a living animal).
Sidebar: Types of Symbiosis
Symbiosis is any type of inter-species relationship that doesn't involve outright killing or eating,
and provides some benefit to at least one of the species. Here's a quick summary of the three
subtypes: mutualism, commensalism, and parasitism.
Mutualism
Commensalism
Parasitism
BOTH species
are helped by the
relationship.
ONE species is
helped, the other is
unaffected.
ONE species is
helped, while
the other
species (the
host) is
harmed.
Example: the
leafcutter ant
"grows" and
tends a fungus in
its colony -- the
ants protect the
fungus, while
the fungus
allows the ants
to digest leaves
for food.
Example: Spanish
moss and live oaks.
The moss only
hangs from the oak,
where it can get
moisture and air.
The oak is really not
damaged at all.
Example:
cowbirds lay
their eggs in
the nests of
other birds
(warblers,
vireos,
sparrows, etc.)
and "trick" the
parents into
raising the
cowbird chicks.
Activity: Classify your Biotic Environment
Choose an organism from the drop-down menu below. From the "point of view" of this
organism, what things are food, predators, friends and competitors? (For this exercise, we'll use
the interpretation of predator from the previous unit: Anything that eats me, even if it's just a
bloodsucker.) Drag the other organisms (in blue) into the four boxes to sort them out. [Note: The
organisms will only snap into their proper place on the chart.] Now try it using a different
organism's "point of view!"
You might notice there's a fine line between "friend" and "competitor" for many organisms -- it
depends on the situation! When different species, like dogs and humans, cooperate to their
12
mutual benefit, it's called mutual symbiosis. Another type of symbiosis is parasatism, like the
mosquito -- one creature (the mosquito) benefits at the expense of another (the victim). A third
type of symbiosis is commensalism, where a creature benefits without really harming or helping
the other species, such as a bird nesting in a tree.
Unit 3b: Resources in the Abiotic Environment
Now it's time to look at our non-living (abiotic) environment and how we might sort these things
from our point of view. People tend to sort out non-living things into the categories of resources,
tools, and threats, plus "stuff we don't care about." The rock you're sitting on could be a
resource (especially if it has a gold vein!) or a tool, which is how you're using it as a seat.
Water's a resource, but if we were drowning, it would be a threat!
If we used this same trick of generalizing to other "points of view" we might run into some
problems. Most organisms really aren't "tool users," so that might be a less useful category. How
would a worm or a mosquito or a tree "classify" the non-living things around itself?
13
Well, the idea of resources is a pretty universal one. When you need some amount of a nonliving thing to survive, it's a resource for you. A tree, for instance, requires sunlight, carbon
dioxide, and soil minerals. Since these resources are available in limited amounts, competition
becomes a very important factor. It's not just between animals — trees compete for sunlight,
their critical resource, in forest environments, and a tree that's completely shaded by another
won't thrive.
Another important category for many organisms is shelter. Water plants or coral reefs provide
shelter for small fish. Rocks provide shelter for snakes and scorpions. The earth shelters worms,
groundhogs, moles, and so on. Shelter can also be considered a resource (and can be competed
for) but it's often considered a different category.
A third and very important category is the weather. Weather is hard to break down into specific
"things" but it has critical impact on the survival of organisms. We can include temperature,
rainfall, snow, storms, and cloud cover in this category. Even ocean environments have a sort of
"weather" including turbidity (how much silt/particles are dissolved), acidity, salinity, and
temperature. When we average weather over long periods and fairly large geographic regions,
we are instead talking about climate. Weather changes rapidly, but climate is fairly predictable
for a region. We would normally talk about organisms that live in a particular area being adapted
to its climate, not its weather.
Sidebar: Climate Change
There are few major environmental issues more misunderstood than "climate change." One of
the most common mistakes people make in understanding the issue of climate change involves
the confusion of weather and climate.
It's possible for human activities to affect the weather (seeding clouds, for instance) but that
doesn't cause much concern to scientists. Weather comes and goes, and is very chaotic and
difficult to predict. Climate, on the other hand, is much more predictable, because it averages
out the "peaks and valleys" of hot spells, cold spells, rainfall and drought, and so on.
A noticeable change in the climate of a continental region would be a major concern -- this can
affect what crops can grow, what trees can live, how much water will be available, and so on. A
global change to the whole Earth's climate could cause a devastating rise in sea level, destroy
major ecosystems, reverse ocean currents, and seriously threaten the survival of people
throughout the world.
People who claim "global warming can't be true -- we've had the coldest winter in years" are
confusing weather and climate. Global warming can, in fact, produce colder winters in some
areas. Nearly all the world's climate scientists are in agreement that our world is on a "warming
trend" and that human activities are implicated in some part. To see the data on this issue, get as
close to the source as possible: NOAA research and NASA studies.
14
Unit 3b: The Niche
So: resources, shelter, and climate define your non-living surroundings. The life around you
contains food, predators, friends (or symbiotes) and competitors. You have a place to live and a
role to play in this environment. Biologists call this "role" your niche. In every identifiable living
environment, or ecosystem (living system), there are thousands of different niches — important
roles that must be filled in order to keep the system in balance. Without decomposers, dead
plants and animals would build up and not return key nutrients to the soil. Without predators,
prey species would overpopulate, consume all available resources, and "crash" from starvation.
Without bees and other pollinators, flowering plants would fail to reproduce.
There are two important points about niches you should know. First, niches are created by
organisms themselves through the complexities of evolution and change. Before plants had
flowers, there was no niche for pollinators. Before there were predators, there must have been
prey — the niche for predators opened up when this ready food source (prey) became available.
The second point is that niches are limited. When two or more species try to compete for exactly
the same niche, one species generally wins, the other loses. The loser may become extinct, or
may adapt to some other, similar niche. Hyenas and buzzards have a similar food niche, but one
has a "ground game" while the other has the "air game."
Sidebar: Think Like a Scientist
Where are the flowers?
Archeologists studying the fossils in the Jurassic period (the age of dinosaurs) were puzzled by
something about the plant "fossils" they found (impressions of leaves, stems, fossilized wood
and such). There were no flowers! The foliage was almost all ferns and large pine-like trees that
pollinate using wind-blown pollen. The Jurassic would have been a tough time for anyone with
hay fever -- pollen would have been everywhere. Flowers, for the most part, are more "polite"
keeping their pollen contained and waiting for a bee to move it around. But there were no
Jurassic bees, either! How did flowers and bees get started?
Scientists often approach a problem with a hypothesis -- an educated guess based on what we
already know. What we knew was that pollen was a food source. Any time there's a food source,
something is going to take advantage of it. The most reasonable guess was: flying insects.
They're small, easily subsist on pollen grains, and can take them right out of the air. So the
simple existence of lots of wind pollen created a niche for an airborne pollen-eater.
So what happens over a few million years to airborne pollen-eaters?
After a while, there are so many of them that the pollen gets a bit scarce, despite the trees' best
efforts. The most successful insects are the ones that go right to the source to get pollen. But now
those trees are in trouble -- they can't make enough pollen to reproduce. Some of the insects,
though, "accidentally" carry pollen on their bodies from one tree to another, helping out the trees.
Over time, these insects learn to recognize the "tastiest" and best pollens, and the most successful
trees and plants are the ones easiest to recognize.
15
See where all this is going? Plants start to develop specialized, colorful "pollen bistros" to attract
their favorite pollen-bearing insects. The best ones start serving up "nectar" drinks as well, quick
energy to get to that next plant. Insects start specializing to collect pollen and nectar from these
new "flowers" and new niches are born.
So to answer the question: "Which came first, the flower or the bee?" our best guess would be,
"Neither." They evolved, step by step, in a complex dance called "co-evolution."
Cool hypothesis, eh? Of course, in order to verify its truth, we'd have to carefully examine the
fossil record and look at what this hypothesis predicts: working up through layers of fossils, we
would first find wind-pollinators, then large numbers of flying insects, then proto-flowers, then
true flowers and specialized pollinators. And yes, that's exactly what we find. This co-evolution
hypothesis is now considered well-supported as an explanation of how flowers came to "bee!"
Unit 3b: The Environment — It's Like an Onion
In the movie "Shrek" our hero compares an ogre to an onion — "We have layers, you see." The
environment's like that, too. We generally start from the perspective of a single organism: this
could be a human being, or a mouse, or a moth, or a single bacterium. Our next "layer" is
generally thought to be a population, which is all the members of one species living in some
geographic region; for example, all the field mice in a large field. Next, we look at the habitat
for that population, which are the physical surroundings (generally abiotic factors) necessary to
support that population. Our next level out is the ecosystem, which includes ALL the
populations in that region, their habitats, and the complex interactions between all these species.
We can talk about the "stream ecosystem" or the "forest ecosystem" in the Southeast USA, or the
unique Galapagos Islands land ecosystem.
After this, the layers get a bit messy. We're now well into the realm of ecology, the study of life's
interactions. Ecosystems blend into each other with no clear dividing lines. Some ecologists use
the term bioregion to talk about areas of the world with unique populations and habitats — the
Sumatran forests, the Amazon rainforest, the Mojave desert. At an even higher level, we can
identify biomes — large world regions defined by climate. And finally, we can talk about our
planet's biosphere, the total area where life is known to exist. Right now, we think our biosphere
extends from about a mile inside the earth's crust out to the limits of our atmosphere. Are there
other biospheres? Or is the whole idea of a "biosphere" silly, and will we find that life exists
even outside of planets and atmospheres? Time will tell.
Sidebar: Additional Resources
Teacher handout describing the world’s major biomes
Middle school and high school lessons plans on ecology and environmental literacy Biodiversity
in a Leaf Pack
16
University of California at Santa Barbara website called Kids Do Ecology
Activity: Layers of the Environment
Let's build an environment "onion" based on the terms used to describe an ecosystem in The
Environment: It's Like an Onion.
For this activity, we'll look at the environment from the point of view of a rabvit. Working your
way from the center outward, drag the labels from the left into the center nested circles. (Hint:
"Organism" goes in the center.) Then, drag the descriptions on the right into the circles, matching
them with the correct labels.
Unit 3b: Assessment
1. A dead tree in a lake would be an example of an abiotic factor in the environment.
True
17
False
2. A type of symbiosis where one organism is helped but another organism is harmed is called:
commensalism
mutualism
predation
parasitism
3. From a cow's point of view, a human being would be considered what?
food source
competitor
symbiote
predator
4. An organism's "role" or "job" in the environment is called its:
character
niche
fitness range
fitness range
5. Which of the following has four levels of the environment listed in increasing size?
population, ecosystem, biome, bioregion
habitat, biome, biosphere, population
organism, population, bioregion, biome
organism, habitat, biome, ecosystem
Unit 3c: Environmental Gradients
We've named our environment. We've classified our environment. Now, suppose we want to
measure our environment. What sort of things can we measure?
18
We can actually measure almost anything in the environment, but let's focus on things that affect
life the most. One obvious measurement is temperature. The Earth's surface experiences
temperatures from about -50°C up to 60°C (about -180°F to 130°F), and most life we're familiar
with can't survive much outside that range. Another is humidity (amount of water vapor in air),
ranging from nearly 0% up to 100%. In the oceans, we could measure acidity (on the pH scale,
from just below 0 up to 14.0), or turbidity (how "muddy" the water is). We could also measure
how much oxygen or CO2 is in the air — average concentration of CO2 is about 390 PPM
(parts per million) in 2010, up from less than 320 PPM in the 1960s.
Each of these values can vary, depending on exactly where in the environment we do our
measurement. For example, we might measure ocean water temperature at different depths, and
we'd find that ocean water becomes colder as we go deeper. No great surprise there...but we
might find some unexpected results if we actually did these tests. There's frequently a "layer"
between 100 and 200 meters down where temperature changes suddenly from fairly warm to
very cold, called a thermocline. This happens in lakes and freshwater environments as well. We
would see this clearly on a graph of depth vs. temperature (see sidebar).
When we take measurements of any abiotic factor along some geographic or time axis and see a
change (gradual or sudden) in the value, we are measuring an environmental gradient. Gradient
just means "a continuous change in a value." An environmental gradient can be a smooth, even
change (for example, pressure changes very predictably with depth) or a more sudden change
(like our temperature thermocline). Gradients can be found on the land and the air, as well. A
source of phosphate-rich rock might be eroded by rainfall and the phosphate nutrients "spread
out" over an area of land, giving a "phosphate gradient" in the soil. At higher altitudes on a
mountain, the average temperature drops significantly, giving a "climate gradient" on the
mountain's slopes. For some mountains, the base can be a tropical rainforest while the top
resembles an Arctic tundra!
All this brings us to our next point: organisms function well (thrive) only within particular
ranges of environmental gradients. No single organism could survive the entire range of surface
temperatures of Earth, but there are certainly those adapted to very hot climates, while others are
adapted to very cold climates. Every species has its "preferred" temperatures, acidity, moisture
levels, nutrients, and so on. Some species can tolerate a broader range on some of these
gradients; others have a very narrow survival range.
Sidebar: Measurements in Science
Measurements are among the most important tools a scientist has. Without measures, we can
never answer the questions of "how much?" These questions are key to experimentation and
discovery of general principles. Until the "how much" questions can be answered, the more
important question of "how?" often can't be answered.
No matter what we measure -- length, time, temperature, strength, force -- we need to
communicate using numbers and well-understood units. If I wanted to measure land area, for
instance, I might measure in acres, a common unit in the USA. But virtually all the rest of the
19
world measures in the metric unit hectares, a square 100 meters on each side (10,000 square
meters).
If I want to communicate with other scientists around the world (and I normally would), I should
convert to our common language of hectares. It's the same deal with other metric units - Celsius
degrees for temperature, liters for volume, and so on. Metric's simply the "way to go" in science.
To
measure:
Use metric
unit:
Cool fact!
Distance
Meter
Originally was the distance from the North
Pole to the Equator (through Paris) divided
by ten million.
Volume
Liter
A cube one-tenth meter on a side holds
exactly a liter.
Mass
Gram
A liter of water masses 1,000 grams (one
kilogram). A 1 cubic cm "cube" of water is
exactly one milliliter and weighs one
gram.
Area
Cubic meter or
hectare
A 10x10 meter square is an "are,” hecto
means hundred, thus, a hundred ares =
hectare.
Temperature
Celsius
degrees or
Kelvin degrees
Again based on water. Water freezes at 0
degrees C, boils at 100 degrees C (at sea
level pressure)
Time
Seconds /
minutes / hours
Our time system, originally from the
Babylonians, is one of the few metric
measures that isn't all multiples of 10.
Force
Newtons
1 N is about the same as the force of
gravity on a small apple (or a stack of
about 10 fig newtons.)
Sidebar: Ocean Thermoclines
The graph shows how ocean temperature typically changes with depth. Notice the graph has its
"zero" depth at the top and numbers becoming more positive towards the bottom. This is
reversed from a "normal" graph, but notice that it makes a better visual "model" this way -- it's
20
like you're looking at a cross-section of the ocean and seeing the temperature drop (move
leftward) as you go lower.
Rather than a smooth, even drop in temperature, we see a sudden change between 100m and
200m; a layer of warm water stays on top, and below 200m the ocean stays very cold. Would we
expect to see dramatically different life forms in the two different layers? Could this "layering"
of water have other physical effects that might be important?
An interesting "factoid" -- thermoclines in water are known to have interesting "sound reflecting"
properties, used not only by whales and other sound-sensitive sea life, but critically important in
submarine warfare.
Activity: What's Your Niche?
The ranges that an organism can tolerate for various environmental gradients help define its niche -where it can live, and with what other organisms. Human beings are unique in our development of
technology that lets us expand our niche and live in places that we couldn't even visit otherwise. Below is
a "before and after technology" table that shows how our niche has expanded from its natural state. For
each factor, can you identify key pieces of technology that enabled the change? Type your ideas over the
question marks.
21
Unit 3c: Zones of Life
A beach is an example of a location with many environmental gradients. In particular, we have
the "wetness" of the land. Beyond the tide line is ocean environment, then we have the wet sand
where the tides wash in, then the drier beach sand, and finally the dunes. We can see distinct
areas here, each with its characteristic forms of life. These identifiable areas along gradients are
called zones, and the process of forming them is called
zonation.
Ecologists would identify beach zones as littoral (just
under water), lower and upper intertidal (low to high
tide areas) and coastal dunes; the image shows more
details of sandy beach zonation. Each zone has distinct
lifeforms; we would rarely find hermit crabs or clams in
the dunes area, while beach grass can't take hold in the
intertidal zone. Mountain slopes are another example of
zonation; distinct types of vegetation and wildlife will be found at different altitude "zones." In
the open ocean, the depth determines how much sunlight can penetrate, and we have zonation
based on sunlight — the euphotic zone has enough sunlight to grow plants, the dysphotic zone
22
is a "twilight" zone, and the aphotic zone is in complete darkness. Organisms thrive in all these
zones but will have quite different adaptations. Creatures below the euphotic zone, for instance,
often have bioluminescent features; they can "glow in the dark."
Sidebar: How Extreme is Extreme?
When we talk about an "extremophile" we are generally talking about a life form that thrives at
an unusual range on one environmental gradient. For example, a thermophile living at
temperatures above 45 degrees C, or an acidophile living at a pH less than 5 would both be
considered extremophiles. But there are a couple of special "more than extreme" classes we've
found. The hyperextremophiles are able to withstand truly amazing extremes in one gradient -hyperthermophiles living in water above 80 degrees C (near boiling), hyperhalophiles living at
33% salinity in the Dead Sea, hyperacidophiles living in mine drainage with a pH of zero.
Another even more interesting class is the polyextremophiles. These organisms thrive at
extremes of more than one gradient. D. radiodurans is a bacterium that can survive extreme
cold, dehydration, acid, radiation, and vacuum. That's some niche! More recently in Argentina,
bacteria have been found that can tolerate lack of oxygen, extreme salinity, and large doses of
arsenic.
The diagram below may help to understand the hyper- and poly- versions of the extremophiles.
23
Unit 3c: Life Makes Gradients
Now, you might think that life is entirely victim to abiotic factors, since we have to live where
the conditions are "just right." And for the earliest life forms on our planet, you'd be correct!
They were adapted to conditions we'd find intolerable. In particular, there was no oxygen at all.
When early plants begin to create their food using photosynthesis, they release a "waste gas"
called oxygen. Have you ever heard the saying "One man's trash is another man's treasure?"
Animals were able to combine molecules of organic "foods" with this extra oxygen from the
atmosphere to release energy, and a whole new class of organisms was born.
Oxygen tends to distribute rapidly throughout the atmosphere, so we don't usually talk about an
"oxygen gradient" (except perhaps at high altitudes). There is another kind of "gradient" at work
here — one based on time. Time gradients show a gradual change in a measurable quantity over
time — sometimes millions of years of time. The amount of free oxygen in our atmosphere grew,
bit by bit, over millions of years. We can find clues to this deep in the fossil record. Before free
oxygen, iron did not "rust." Geologists have identified deep layers of iron-rich rock that show the
first signs of oxidization, or rust, and have thus established evidence for when we first had
significant free oxygen in the atmosphere (around 3 billion years ago).
One "time gradient" that's causing a lot of concern among climate scientists today is our carbon
dioxide gradient. CO2 concentration has risen very rapidly in our atmosphere, over a 12%
increase since the 1960's, with the most likely explanation being our burning of huge amounts of
fossil fuels. Finding this dramatic a change in only a century is unprecedented — natural
processes would take millions of years. There are many potential effects of higher CO2 levels,
including the "greenhouse effect" and suspected linkage to warmer Earth surface temperatures.
Moving upwards on the "CO2 gradient" also favors certain species at the expense of others.
Vines, especially toxin-producing vines such as poison ivy, grow much faster in a CO2-rich
atmosphere. Could this possible accelerated growth of vines strangle our forests? Maybe, or
maybe natural processes will adapt and bring things back into balance. The greatest concern is
that we are changing this gradient so rapidly that we can't predict all the effects on our
biosphere...and that is what has a lot of people worried.
Sidebar: Additional Resources
NASA’s Eyes on the Earth Website allows users to view global changes in temperatures, carbon
dioxide emissions and more http://climate.nasa.gov/
NASA’s Climate Kids website features educator resources, online games, and videos
http://climate.nasa.gov/kids/
Unit 3c: Life Begets Life
24
Living things change their environment. The first photosynthetic bacteria set us on the path to an
oxygen-rich atmosphere, and our human industry has increased carbon dioxide levels. These
abiotic factors, in turn, affect life by altering niches. But this process can be seen in many, many
other situations. Life seems to build itself up, layer by layer, in a process called ecological
succession.
Imagine a barren, lifeless rock — maybe a recently cooled lava flow from a volcano. How can
life take hold on such a surface? The first thing that happens is that spores and bacteria settle on
the rock; they are everywhere in our atmosphere. Rust-like patches of bacteria form, and soon we
see lichen, a combination of a fungus and algae. The lichen helps collect dust and sand grains in
"pockets" in the rock and provides nutrients, and after a while, tiny weeds and grasses can grow.
From there it expands to small rooted plants and bushes, and then small trees. The roots crack the
rock and begin to reduce it, step by step, to soil. Each "layer" of life paves the way for the next,
building the niches for more diverse species. Understanding the "time gradient" of succession
can help ecologists know how "old" a particular ecosystem is, or how long it's been since the
most recent disaster like a fire, flood, or mudslide.
25
Sidebar: Additional Resources
Worksheet discussing ecological succession
Lesson plans on ecosystems including ecological succession
Unit 3c: Assessment
1. A thermocline is a region in the ocean where temperature is changing very gradually.
True
False
2. In a lab a scientist is testing water samples by shining light through them and reading a light
detector. What is the scientist most likely measuring?
temperature
salinity
turbidity
density
3. An environmental gradient is a change in some abiotic factor measured over:
a geographic (distance) range
a span of time (time range)
a range of masses
either geographic or time range
4. The best explanation for how our planet got an oxygen-rich atmosphere is:
it was delivered by a meteor collision
it was released by chemical reactions in the rocks
it was created by early life through photosynthesis
it came from the oceans
5. The stepwise "building" of life in layers, such as lichen, weeds, shrubs, and trees, is called
ecological:
26
succession
layering
grouping
design
Unit 3d: Extraterrestrial Environments
"Aliens from another planet!" has always been a subject of fascination and awe. In science
fiction (including nearly all SF movies) the "aliens" are humanoid, generally with advanced
weapons or "special powers." Why exactly is it that we seem to think that intelligent aliens will
look (or act) anything like human beings? Is all intelligent life based on a bipedal, four-limbed
single-head "standard model?"
Maybe we just tend to view all life from a privileged perspective, and since we seem to be the
"top dog" life-form on our planet, we assume that model will hold elsewhere. The evidence from
our fossil record and our best evolutionary models don't support that, however. We seem to be an
evolutionary "special case." Why exactly did primates get the go-ahead for big brains and
reasoning? Why not bears, or wolves, or squid, or insect swarms? The simple fact is that most
primates stayed, well, primates. The gorillas and chimps and bonobos are pretty smart and social,
but never quite made that "leap" into advanced language and civilization. Our leading hypothesis
is that, sometime around 4 to 6 million years ago, a group of primates were being "starved out"
of a dwindling forest, had to adapt to grasslands, developed a habit of walking upright, and
gradually adapted their tree-climbing hands into object-manipulating hands. But it didn't have to
happen that way.
The octopus is a fearsome creature in its own environment. Its eyes are several times better than
ours. Eight precise limbs can manipulate objects as well as attack. It can adjust its coloration and
texture to hide. Plus, it exhibits surprising intelligence. (Check out these videos) Why is it that
we don't have civilizations, language, and technology built by octopus-evolved creatures? The
short answer: luck of the draw. Humans got there first. That doesn't mean, though, the
"intelligent octopi" aren't coming — our leap to civilization happened in an eye-blink of time,
evolutionarily speaking. It might take the octopi another million years, which we think of as
"forever" but is really a pretty quick evolutionary development!
So what's really out there? Are the intelligent octopi or insect-brains ready to greet us on some
distant star's planet? Where do we look for life, and what kind of life might we predict will be
there? Science lives to predict, but we only have one planet's worth of evidence, which really
isn't a lot to go on. We do know one thing that seems "solid bedrock" that we can generalize
about life, and it seems a good place to start: Life adapts to its environment. So if we want to
find where life might exist, we must find out as much as we can about what other environments
are "out there!"
27
Sidebar: Additional Resources
The Search for Extremophiles on Earth and Beyond
Scientific American article asking what aliens will look like
National Geographic gallery of images illustrating what alien life might look like
Unit 3d: Our Solar System Real Estate
So, where in our own solar system, besides our own dear planet, should we start looking for life?
"Traditional" wisdom used to say that we should only consider planets in the "habitable zone" of
our star; that is, those getting just the right amount of sunlight to possibly support liquid water.
That would pretty much be Venus, Earth, and Mars. But our new knowledge of extremophiles
has revealed that sunlight isn't necessarily the key factor. There's also volcanic heating from
inside a planet (or even a moon) that can provide energy for life. Another thing we've always
looked for (and this one's pretty important) is water - preferably liquid water.
We can't say for sure that life is impossible without water. Life as we know it is water-dependent
(even though some life forms can survive for many years in a dormant state without water). It's
possible, though, that other liquid solvents like ammonia or liquid methane might support a
different DNA-like molecule and enable some form of life. Our best bet, though, seems to be
water, since it would potentially support life of the kind we're most familiar with. Where might
we find some?
Sidebar: Additional Resources
NASA’s Planet Quest site featuring a count of how many exoplanets have been discovered, an
atlas guide to newly discovered planets, timelines, videos and more
http://planetquest.jpl.nasa.gov/
NASA Kepler mission home page covers Kepler’s mission to find habitable planets
http://www.nasa.gov/mission_pages/kepler/main/index.html
NASA’s solar system web page for kids with interactive activities, downloads, models and more
http://solarsystem.nasa.gov/kids/index.cfm
Unit 3d: Is the Red Planet a Dead Planet?
Mars, our second closest neighbor (next to the boiling-hot Venus) has always been a fascinating
candidate for life. While the "little green men" are an unlikely possibility, astronomers for
28
decades have noted the strange "canal-like" structures on the Martian surface and suggested them
as evidence for a watery surface, perhaps millions of years in the past. Most scientists dismissed
the claim, but recently, NASA's Odyssey spacecraft has found clear factual evidence of water ice
on Mars — lots of ice. An entire ocean of ice. Could this have been liquid at one time? Could it
have supported life, and if so, are there still fossilized traces of this life, or even still-living lifeforms in a dormant state? What's happening underground in deep cave formations — are there
still traces of geothermal energy inside Mars, melting ice to liquid water and supporting a
Martian ecology?
Questions abound, and answers are slow to come. But Mars is "relatively" easy to get to (don't
expect a manned mission anytime soon, though, the several-month flight time is a challenge). So
we can use robotics and instruments to investigate further, looking for evidence of past or present
life. We'll probably be looking for bacteria or other microbial life. It's not that multi-celled
eukaryotes couldn't exist there, but they are a rarity on Earth compared to the massive numbers
of bacteria or archaea (prokaryotes).
Sidebar: Additional Resources
NASA’s website for the Mars Exploration Program where you can see a movie of a real Martian
sunset, view a map of where the Mars rovers are located, and get an unprecedented view of the
planet with images from the Mars Reconnaissance Orbiter http://mars.jpl.nasa.gov/
Mars information for kids http://www.kidsastronomy.com/mars.htm
Mars educational resources for teachers from NASA
http://mars.jpl.nasa.gov/participate/marsforeducators/
Unit 3d: Europa - the New Hope-a!
Europa, the fourth largest moon of Jupiter, is an unusual beast. Most moons this size (slightly
smaller than our moon) are pock-marked with craters and dry as a bone. But the surface of
Europa is relatively smooth. How can this be? Europa certainly gets hit by as many asteroids as
any other moon...
Unless...those asteroids are impacting into ice, with a layer of water beneath. Ice over liquid
water would be "self healing" and quickly smooth over most impacts. Could there be a giant
ocean just beneath the surface of Europa? The answer seems to be YES. The 1999 Galileo
mission discovered "cracks" in Europa's surface very similar to ice-plates on Earth. The chemical
analysis signatures all point to a vast sub-surface ocean, one which is clearly a candidate to
harbor life!
Several exploratory missions to Europa have been proposed. The simplest and cheapest is to flyby Europa and drop a "bomb" that would vaporize a chunk of the surface (and perhaps deep
water), then collect some of the particles from space and return home. It's not our best chance to
29
discover life, but we would learn a lot about the chemistry, which can provide clues. Another,
more intricate mission, would involve landing a "submarine" probe that could melt through the
ice and send back images and detailed analysis. It would be critically important to sterilize the
probe, to make sure we didn't accidentally introduce Earth-based organisms.
Again, scientists would be delighted to find microbes - something resembling bacteria or
archaea. However, in an ocean environment, even a very cold ocean, complex life can develop
quickly, and we might find our probe swimming with Europa-sharks and "Europaccudas!"
Sidebar: Additional Resources
Europa information and images from NASA
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Europa
Article on where we should look for life next: Europa vs. Titan
http://dsc.discovery.com/news/2009/02/09/titan-europa-life.html
Images of and information on Europa http://www.seasky.org/solar-system/jupiter-europa.html
Unit 3d: Does Mighty Titan Have Life to Frighten?
Titan, the largest moon of Saturn, is not exactly the first place you might look for life. There is
definitely water there, but it's unlikely to be liquid, since surface temperatures are around
-180oC. There is a lot of carbon and hydrogen, but little or no free oxygen. It does have an
atmosphere, but it's nearly all nitrogen with some methane (CH4). The fact that it does have an
atmosphere, along with volcanic surface features, has made it a subject of fascination for
astrobiologists for many years, though.
In 2004, NASA's Cassini-Huygens probe actually deployed a "lander" which penetrated Titan's
thick atmosphere and parachuted to the surface. It was the most distant landing probe ever
deployed, and the picture shown represents the most distant "ground" surface ever photographed.
The "rocks" in the photo are actually water ice. Another discovery by this mission was that Titan
had giant surface "lakes" of liquid methane!
Now, liquid methane isn't exactly the sort of "swimming pool" we'd expect to support life. But
what if it did? Is there any kind of life that could survive in liquid methane, based on our
knowledge of chemistry? Researchers Chris McKay and Heather Smith published a paper in
2004 speculating on just this topic. They proposed that a methanogen which used hydrogen gas,
rather than oxygen, for its "respiration" might live and thrive in such an environment, and might
become widespread.
Now, just like early photosynthetic life altered Earth's atmosphere, making it oxygen-rich, such a
"hydrogen-breather" could alter Titan's atmosphere over time. So McKay/Smith went out on a
limb and made a prediction. They said that if this type of life was common on Titan, we would
30
see less hydrogen gas, acetylene, and ethane at the surface (lower atmosphere) of Titan than
chemical models would predict. As other scientists continued to analyze the Huygens/Cassini
data, it became clear that's exactly what we were seeing. Something is apparently combining
acetylene and ethane with hydrogen and turning it into methane. Could this be a life form? Or is
it some unknown chemical process?
Like Europa, there's also the possibility of liquid water oceans, but they would have to be deep
underground under immense pressure, and probably rich with ammonia. Life in a cold, pitchblack vat of floor cleaner under crushing pressure? We're not ruling it out...
Sidebar: Think Like a Scientist
McKay and Smith's paper essentially proposed a hypothesis -- an educated guess about
something that might or might not be happening. To do this, they combined background
information from chemistry and biology to get to a "plausible" biochemical model for life in a
methane/hydrogen environment. Then they took the most important step: they made predictions.
When investigating the unknown, these type of predictions often help drive scientific
investigations. McKay/Smith's hypothesis and predictions motivated other researchers to look
more closely at the low-atmosphere chemistry of Titan, and they found verification of the
predictions. This is the strongest kind of support for a hypothesis, though it doesn't mean it's
necessarily true.
Good science always predicts. In fact, that's what makes science useful to us -- all our
technology, all our best theories, all our core knowledge comes from the ability to predict what
will happen based on conditions. The diagram below shows the process of developing a
hypothesis into a theory based on predictions.
31
32
Unit 3d: Even More Real Estate!
There are other life supporting candidates, including Enceladus, another of Saturn's moons, from
which we've seen plumes of liquid water emerge. As we look beyond our own solar system, we
have now detected evidence for literally thousands of extrasolar planets, orbiting distant stars.
Without Star Trek technology, we might find it impossible to actually visit them, but perhaps we
could detect some chemical "signature" or even a broadcast from one!
Finally, there's always that possibility of finding life in outer space between planets. If water
bears and D. radiodurans (from our previous unit on extremophiles) can withstand outer space
for hours or days, isn't it reasonable to think that some super-hardy bacteria or "space seed" can
move between planets? Could this even be a way to move life between planets? Meteorites are
always striking planets and moons, blowing off particles that could potentially end up landing on
another planet. Could this even be the way life got started on our own planet Earth? This curious
hypothesis is called the panspermia theory, as opposed to the idea that life started independently
from chemicals on our own planet, called the abiogenesis theory. This is a huge debate within
astrobiology. Which will be proven correct? Well, what predictions do you think each theory
might make?
Sidebar: Additional Resources
NASA information on Enceladus
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Enceladus
Information on meteorites and comets and how they might carry organic material
http://web.mit.edu/afs/athena.mit.edu/user/r/e/redingtn/www/netadv/bioast/clash/article.html
The National Center for Science Education offers resources and information on the teaching of
evolution in public schools http://ncse.com/
Activity: Abiogenesis vs. Panspermia:
SMACKDOWN!
Only one of these two theories can be true. Either Earth-life started from "scratch" here on Earth
(abiogenesis) or it began somewhere else and was carried here (panspermia). We could include
some other theories: life could have been placed here fully formed (creationism) or designed in a
guided way (intelligent design). But we still get back to the question: created here or moved
here? Any theory worth its salt will make some specific predictions.
On the right-hand side of the chart below are some specific predictions. Try to classify them by
which theory you think they would support: abiogenesis or panspermia, then drag them into the
proper column on the chart. When you have classified each prediction, hit done. Any incorrect
answers will appear in red.
33
Unit 3d: Assessment
1. Evidence that Europa may have vast underground seas of liquid water includes:
a lander probe detected ice on the surface
canals on the surface of Europa
there are signs of tidal action
the relatively smooth surface suggests "healing" of craters
2. Titan appears to have vast seas of liquid methane.
True
False
3. What is the best explanation of how a hypothesis becomes an accepted theory?
34
the hypothesis is published, and makes sense to many scientists.
the hypothesis makes specific predictions, which are later verified to be true
the hypothesis provides a more detailed explanation of a known phenomenon
the hypothesis becomes the most popular explanation among science writers.
4. The idea that life on Earth may have started elsewhere and been "seeded" here by meteor,
space dust, etc. is called:
abiogenesis
Gaea hypothesis
panspermia
invasion theory
5. We now have clear, definite evidence that there is water ice on the surface of Mars.
True
False
Unit 3: Resources
NASA's NEEMO Mission
Informational Website from NASA
NOAA Ocean Explorer
Informational Website from Ocean Explorer
Goddard Multimedia - Marine Food Web
Animation from NASA/Goddard Space Flight Center
NASA Earth
Informational Website from NASA
Discovery Channel's Blue Planet
Informational / interactive Website from Discovery Channel
Animal Planet's Blue Planet
Informational / interactive Website from Animal Planet
EPA Ecosystems
Information and resources from the Environmental Protection Agency.
35
Limits of Organic Life
Book available for purchase from the National Academies Press
Planet Quest
Informational Website from NASA
Astrobiology Magazine
Informational articles from Astrobiology magazine
NOVA Origins
Inquiries, interviews, interactives and slide shows from NOVA
NASA Climate Change
Informational Website and interactives from NASA
Unit 3: Lesson Plans and Activities
Learning Planet Sizes
Grades K-4. Students use the concepts of greater than, less than, and equal to, in order to classify
student height, object size, and planet size, then build scale models of the planets based on their
discoveries of planet size. Lesson plan from NASA MSU-Bozeman CERES project.
Investigating the Changing Polar Ice Caps
Grades 5-8. In this activity, students download NASA Hubble Space Telescope (HST) images of
the Martian polar ice caps in summer and winter and use image processing techniques to
compare Martian and Earth polar ice caps. Lesson plan from NASA MSU-Bozeman CERES
project.
Analyzing Meteorological Data From Mars
Grades 5-8. Students compare real-time Earth and Mars measurements for temperature, wind
speed, humidity and atmospheric pressure by accessing Internet-data resources from NASA.
Lesson plan from NASA MSU-Bozeman CERES project.
Finding Extrasolar Planets
Grades 9-12. Students plot and analyze NASA data to determine the period of an invisible planet
orbiting a wobbling star. Lesson plan from NASA MSU-Bozeman CERES project.
NASA Astroventure (Search for and Design a Habitable Planet)
Use a computer simulation on this interactive website from NASA to design a planet habitable to
humans but not exactly like Earth.
Interactive Biogeochemical Cycle (PDF)
Grades 5-8. In this lesson, students will learn that microbial mats are entire ecosystems where
different organisms perform different roles (producer, consumer, decomposer) in the ecosystem.
36
Students will also gain an understanding of how microbial mat ecosystems contributed to the
Earth’s biosphere.
Project WET
Play interactive computer games about water that teach kids how critical water is to life. Other
topics covered by the games include habitats, ground water, the water cycle, and water
conservation.
Water Festival Game
Hydration Game
Project Wild
Project Wild has many educational resources including the Project WILD K-12 Curriculum and
Activity Guide. It focuses on wildlife and habitat. The activities are designed for integration into
existing courses of study and even include evaluation suggestions.
Project Learning Tree
This website includes curriculum for preschool through high school on topics such as energy and
society, forest ecology, biodiversity, forests of the world, and more.
Ocean Planet
The Smithsonian created six lesson plans to go along with its exhibit Ocean Planet. "Sea Secrets"
explores ocean geography; "Sea Connections" looks at the plants and animals that live in
different marine ecosystems. "Ocean Market" identifies and values many products of the seas.
"Pollution Solution" examines the effects of an environmental crisis. "Stranded Along the Coast"
explores both natural and human causes of animal strandings. Finally, "Reflections on the Sea"
explores the influence of oceans on language and literature.
Geography for Kids
This website for kids features information on topics such as the atmosphere, the biosphere,
climate, and more. There are interactive quizzes that cover each topic so students can check their
knowledge. The website also contains many interactive panoramic photos as well as, live
cameras and real-time monitors.
Biology for Kids (Systems)
This website for kids features information on topics such as cells, microorganisms, invertebrates,
and more. There are interactive quizzes that cover each topic so students can check their
knowledge.
NASA Mission to Planet Earth (PDF)
Grades K-3. This NASA guide is for teachers on how to teach Earth system science. To
understand the way the Earth system works, students first must learn what these components are
and then examine ways that they interact and change. To do this, they will build terrariums as
models of Earth. Throughout these four units, students will learn how scientists study Earth’s
system to understand human-induced and natural changes.
Connecting Ecosystems & Climate (PDF)
37
Grades 9-12. The connections and interactions between the abiotic and biotic components of
ecosystems and climate are introduced and explored in this lesson. A hands-on sorting activity,
physical webbing and concept mapping are used to encourage students to directly explore the
interaction between abiotic and biotic components through the lens of climate change and the
potential impact on ecosystems.
NASA Environmental Lesson Plan Archive
Lesson plan archive from NASA with topics such as climate, energy, photosynthesis, and more.