The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
For YSP Volunteers: How to Run this Activity
Logistics
Number of Volunteers: minimum 4 volunteers, unless you remove 1 or more stations
(see the module text)
Amount of Set-up Time: Varies, including: driving time to Missouri Botanical Garden,
preparation gathering loops (and journals, in the case of the Costa Rica Project); potentially time
getting free group passes once arriving at the Garden.
Amount of Running Time: 9:00 am to 12:00 pm for a normal demo outing; however, for
Costa Rica Project students who are also journaling, they can be at the Garden for longer, from
9:00 am to 2:30 pm.
Module Overview
Embracing experiential learning, we take a field trip to Missouri Botanical and tour the
Climatron, the giant dome-shaped building housing nearly 3,000 exotic plant species. This module
therefore stands as an extremely unique opportunity to tour a tropical ecosystem within our very
own St. Louis. We recommend spending a three-hour time period at Missouri Botanical Garden, in
order for us to accommodate for ample learning and travel time within the Garden. However, the
Eco/Evo Teaching Team is willing to work with a shortened schedule. We also strongly
recommend planning for this module on a Wednesday or Saturday morning, since admission to the
Garden is free before noon on these days. Ideally, we set up a 9:00-12:00 visit either Wednesday
or Saturday morning; lunch can be eaten afterwards in Missouri Botanical Garden’s Sassafras
Cafe.
Curriculum Links
Missouri Science Standards
3.1.E. Biological classifications are based on how organisms are related. a. * Explain how
similarities used to group taxa might reflect evolutionary relationships (e.g., similarities in DNA and
protein structures, internal anatomical features, patterns of development). b. * Explain how and
why the classification of any taxon might change as more is learned about the organisms assigned
to that taxon
4.3.B. Reproduction is essential to the continuation of every species. a. *Define a species in
terms of the ability to mate and produce fertile offspring. b. Explain the importance of reproduction
to the survival of a species (i.e., the failure of a species to reproduce will lead to extinction of that
species).
4.3.C. Natural selection is the process of sorting individuals based on their ability to survive
and reproduce within their ecosystem. a. Identify examples of adaptations that may have
resulted from variations favored by natural selection (e.g., long-necked giraffes, long-eared jack
rabbits) and describe how that variation may have provided populations an advantage for survival.
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http://ysp.wustl.edu
Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
Goals
The students intimately explore the tropical plants through four “learning stations” which we
strategically placed around the Climatron and which include: 1. Evolution of Plants, 2. Adaptations,
3. Leaves and Flowers, and 4. Growth Forms. Multiple instructors allow for the class to explore
topics hands-on and in small groups. Rather than lecturing at students, we use the real life forms
around us to cover topics such as the transition from ancient to modern plants and associated
plant classification, the way that plants use their resources, and the wide variety of familiar edibles
including pineapples, chocolate, and rice. We also cover pollination, reproduction, and the basics
of photosynthesis and cellular respiration.
Materials
Worksheet, so that you remember what your topic is, where the Climatron station is, and the
agenda; a watch or another way to manage time during the station rotation.
What to Expect
Based on past experience running this activity, you can expect…
This module is performed best with students at the high school or upper middle school levels.
Warn students that the Climatron can be very hot during the day – around 75 or 80° F! Therefore,
students should dress accordingly. Each volunteer should read through this handout very well, so
that he or she has a good idea for how this module flows. Each station volunteer, who teaches
one of the Climatron stations, should maybe even visit the location of the station, before the day of
the field trip, so that he or she knows where the plants are that you will be discussing.
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
Station Topic Information for each Station’s Volunteer Teacher:
1. STATION EVOLUTION OF PLANTS
What is evolution? Evolution generally speaking is change over time, and we can quantify this change in
different ways. We can look at changes in form (phenotypes) over time, or we can look at changes in
genotype frequencies over time. However we decide to define evolution, we use this theory to understand
the history of life on Earth and why we see the diversity of organisms on Earth today.
Building complexity. A general trend that scientists notice is that over evolutionary history, life on Earth has
become increasingly complex. Life started with single-cell organisms in the ocean and as natural selection
began to act on life-forms that were more adapted to their environments, increasingly complex organisms
came into being. The next step was the evolution of multicellular organisms, and some of these species
eventually evolved the capability to gain energy from sunlight. These algae were the precursors to the first
plants!
If algae came before plants in evolutionary history, why do we still have algae today? This is a common
misconception of how evolution by natural selection works! Certain algae may have gone on to evolve into
the first plants around 500 million years ago, but this does not mean that all algae species did. Natural
selection only acts on what is more fit at the given time in that environment, so major changes in form (like
from algae to plants) are extremely rare and take millions of years to occur. Though algae that we see today
are definitely less complex organisms than plants, it does not mean at all that they are any less adapted to
their environments. This is how we have such amazing biodiversity today, especially within the plants!
Life as a land plant. When plants first evolved on land, they faced some challenges that aquatic plants or
algae did not face. First, they had to be able to derive nutrients from the soil and maintain stability. Second,
they needed to also be able to take in carbon dioxide from the air and bring in sunlight. All land plants also
have a common characteristic, alternation of generations.
Four major plant forms in evolutionary history:
1.
The least complex land plants we see today, and probably the first to evolve on Earth are the
mosses, along with their companions, liverworts and hornworts, collectively known as bryophytes. Point out
moss species near station, and allow students to make some observations. Ask students if they have seen
mosses before and where they saw them.
These are land plants which do not have seeds or flowers. Bryophytes reproduce with spores, which you
may be able to see sticking up from stalks if you look closely enough at them. Bryophytes lack vessels, so
they must remain small in size to allow water to disperse their seeds. These plants have two generations, a
sporophyte and a gametophyte. The gametophyte is what we are seeing when we see mosses growing and
is their dominant generation. The sporophyte is underneath the gametophyte and is rarely seen, but it is the
generation that produces the spores.
2.
The next group of land plants to evolve was the pteridophytes, which include ferns and their allies.
Point out fern species near station, and allow students to make some observations. Ask students if they
have seen ferns before and where they saw them. Note particularly the major differences between mosses
and ferns. These are land plants which contain vascular tissue called Xylem and phloem, which were
missing in bryophytes. Xylem are used to transport water and nutrients from the roots to the leaves, and
phloem sugars and macromolecules from the leaves to the roots. Pteridophytes also reproduce by spores,
which you often can see if you turn over a mature leaf on a fern. The dominant generation of ferns is the
sporophyte, the fern plant that we think of, which the gametophyte generation is very small.
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http://ysp.wustl.edu
Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
3.
The next group of land plants are the gymnosperms (which means “naked seed”), which include
most notably conifer trees, but also species like gingkoes and cycads. Point out gymnosperm species near
station, and allow students to make some observations. Ask students if they have seen gymnosperms
before and where they saw them. Note particularly the major differences between ferns/mosses and
gymnosperms. These plants produce seeds, not spores, which are contained inside a cone. These seeds
provide the developing plant with nutrients and a protective coat. Gymnosperms produce pollen cones that
contain the male gametes, the pollen grains. These are carried by wind to the female cones, where the
seeds are stored and fertilization occurs. Since this process is fairly inefficient, male cones produce far
more pollen than necessary to ensure fertilization occurs. Once fertilized, seeds are dispersed without the
use of an ovary, which is why they are called “naked seeds.” The dominant generation of these plants is
also the sporophyte generation.
4.
The final group of land plants, and also the largest and most diverse, are the angiosperms, or
flowering plants. Anything not mentioned in a previous group is included in this one! Point out angiosperm
species near station, and allow students to make some observations. Ask students if they have seen
angiosperms before and where they saw them. Note particularly the major differences between
gymnosperms and angiosperms (there’s pretty much just the flowers). These plants also produce seeds like
the gymnosperms, but the seeds are protected inside an ovary, which becomes the fruit. The flowers are
helpful in attracting pollinators so spreading their gametes to other plants does not require scattering pollen
into the wind. Fruits also help disperse fertilized seeds as they often attract animals, which will carry them
long distances.
DISCUSSION QUESTIONS:
·
How did we/do scientists group species together? What are some other ways than just similarities in
structures that scientists today might be able to group species?
·
Why do you think angiosperms are the biggest group of the land plants? Can you think of specific
adaptations that have allowed them to become so successful?
·
Since we know what plants require to survive, can you think of some habitats on Earth that plants
could not exist? Which of the four forms of plants we talked about are probably the best at finding new
habitats?
·
Can you think of some examples of habitats that are dominated by one of the four types of land
plants we talked about?
·
Why is it that we are able to see so many different kinds of plants occupying the same habitats?
2. STATION ADAPTATIONS (AND EDIBLES)
Adaptations are special features that organisms have developed over many generations. These
adaptations allow organisms to reproduce, survive and live in conditions that otherwise would be difficult or
impossible. In the case of plants, adaptations allow them to live in particular habitats (e.g. flooded areas),
take advantage of mutualistic relationships (plant-insect interactions) and retreat predators (protect them
from predators). The tropical rainforest can reach temperatures between 80Fº to 90Fº with rains about 80 to
180 inches per year. Flooded areas are common as a consequence of the heavy rains which at the same
time promote soil erosion. Soil minerals and organic nutrients are constantly soaking into the ground rapidly.
Plants in the tropics not only use up any organic material quickly resulting in poor soils, but also have
adaptations that allow them to live in this environment.
Shallow roots are an adaptation for trees in the tropics, however this type of root system demands
extra support. Buttressed roots not only have the role of support, but also have a nutrition role. These roots
are lateral extensions that grow out from the base of the trunk as high as 15 ft above the ground giving the
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Climatron Tour at Missouri Botanical Garden
tree extra support. At the same time, these buttressed roots increase the tree's cover area allowing nutrient
absorption.
Tropical forest is surrounded by rivers, resulting in areas where trees grow at the water's edges
which are subject to flooding. This requires trees to have extra support and help oxygenating when waters
are high, both functions are met by stilt roots. These roots grow out of the trunk or from other stilt roots.
Once the tip of the stilt root reaches the ground it will develop an underground root system which then
develops further stilt roots which will grow arching into the air to again connect the tip to the ground and
form a new root system. This process happens over and over, providing the required support to the tree. In
areas with low oxygen, the gas exchange occurs through the lenticels found in the roots.
There are several tropical plants that we are very familiar with that have developed adaptations,
these are coffee and rice. The coffee plant (Coffee arabica) uses the chemical compound called caffeine as
a repellent. Once an insect feeds from the coffee plant it stays away because of the effects of caffeine to the
insect’s neural system sometimes causing death. Caffeine also protects the coffee plant underground from
fungi and bacteria.
Rice's adaptations are related to the partly submerged paddy fields where it grows. These fields
become very muddy as a consequence, and have decreased oxygen concentrations. In these areas,
oxygen is mainly concentrated on the surface for which rice has adapted to have abundant shallow roots.
On the other hand, for oxygen to reach those roots that are in deep areas where there is a lack of oxygen
(anaerobic respiration), rice stems have adapted to have many air spaces allowing the distribution of
oxygen to the cells of those roots. Under anaerobic respiration, there is production of ethanol which is toxic
for most plants, but rice's root cells have adapted resistance.
An interesting adaptation against herbivory is the leaf movement of the "sensitive fern" (Mimosa
pudica) known as seismonastic movement. Stimuli such as light, touch, heat or wind over some regions of
the stem produces the release of chemicals, like Potassium, which forces the water to go out the vacuoles
making the plant's cells lose their pressure and collapse. As a consequence, the difference in pressure in
the different regions of the cells causes the closing of the leaflets. It is presumed that when leaflets are
closed they are less attractive to insects which start looking for more "normal" leaves.
DISCUSSION QUESTIONS
Adaptations
Describe climatic conditions in the climatron (hot and humid) as an example of a difficult environment to live
where natural selection can act. Add to the equation that in the tropics it rains a lot making soil poor and
nutrients soking quickly. Show the litter material in the soil and compare it with the litter in the tropics. How
can plants live in such a difficult place? Special features called adaptation have evolved during many
generation allowing plants, in this case, to live in the tropics. This is true for any harsh environment, where
plants have adaptations that allow them to live in those places. Point out the different parts of a plant to
make them remember plant anatomy. Which parts of the plant can show adaptations? Any part can develop
an adaptation!
Root adaptation-Buttressed roots
Show buttressed roots, why are buttressed roots important? Trees in the tropics have shallow roots since
most of the nutrients are on the surface, so big trees need extra support. Buttressed roots have a nutritional
role since they increase the tree's coverage area allowing the absorption of more nutrients.
Root adaptation-Stilt roots
Tropical forests are surrounded by rivers, so some trees are subject to constant flooding. Show stilt roots
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Climatron Tour at Missouri Botanical Garden
and mention that they are common in flooded areas. What is the role of stilt roots? Are there any differences
or similarities to the buttressed roots? BOTH!! Stilt roots not only offer support to the trees in these areas,
but also help the plant with gas exchange when there is a lack of oxygen (lack of water flow) through
lenticels. Point out lenticels in the stilts roots!!
Plant adaptation-Coffee plant
Walk to the coffee plant and ask, why do we like to have a cup of coffee in the early morning? because it
wake us up. What is the chemical compound that makes this possible? caffeine!! Can you imagine what
would happen if an insect had a high dose of caffeine? Coffee uses caffeine as a repellent, once the insect
eats part of the coffee plant, caffeine will act on the insect's neural system causing harmful consequences
and sometimes death.
Stem adaptation-Rice stems
Show rice and point out that rice grows in manmade flooded areas or paddy fields, why does it not have
buttressed or stilt roots? It is not as tall as the other plants!! It does not have lenticels, then how does it get
oxygen? These fields became very muddy as a consequence, the oxygen concentration decrease rapidly
mainly concentrating on the surface for which rice has adapted to have abundant shallow roots (show these
roots). The most important adaptation is on the stems (point out the stems). Rice's stem has adapted to
have many air spaces allowing the distribution of oxygen to the cells of those roots.
Leave adaptation-sensitive fern
Touch the sensitive fern, why does it close its leaflets (leaf like)? not clear, but it is presumed to reduce
insect attack. Do leaflets close only when you touch them? NO. Leaflets will respond to any stimuli such as
light, heat or wind. This stimuli will produce the release of chemicals, which will break the wall of secondary
cells (vacuoles) making their water go into the plant's primary cells losing their pressure and collapsing to
finally produce the leaflets to close.
DISCUSSION QUESTIONS—ANSWER KEY
What is an adaptation? Adaptations are special features that have evolved during many generations that
allow organisms to live in harsh environment.
What is the main function of buttressed roots? Since most of the nutrients in the tropics are on the soil
surface, trees have adapted to have shallow roots which demand extra support which is given by buttressed
roots.
What other function besides support is given by stilts roots? Help with oxygenation. Trees that grow in
flooded areas can face low levels of oxygen due to the lack of water flow, in this case the lenticels in the
stilts roots allow gas exchange.
How is caffeine used by the coffee plant in nature? As a repellent. Insects that eat part of the coffee plant
ingest caffeine which acts on the insect's neural system causing harmful effects and sometimes death.
What is rice's main adaptation? Since the fields where rice grows become muddy quickly, there is a rapid
decrease of oxygen. Roots that are in the deep area get oxygen through the stem where there are big air
spaces that allow the distribution of oxygen to the cells of those roots.
Who can explain to me the mechanism that allows the sensitive fern to close their leaflets immediately?
After a stimuli such as light, touch, heat or wind, chemicals will be released and vacuoles walls will break,
making their water go into the plant's primary cell losing their pressure and collapsing. This will cause the
leaflets to close.
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Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
3. STATION LEAVES AND FLOWERS
Energy Capture through photosynthesis – the tremendous importance of plants
Leaves are oriented around a tree to absorb light and capture the energy from light in a process called
photosynthesis. Point to the orientation of leaves around a trunk, etc. to show their ideal position for
absorbing light. Why are plants SO important? There is nothing like them that can capture the energy that
WE need to live! Only plants and few bacteria can get this energy!
Plant anatomy – leaves
Most photosynthesis occurs in leaves! That is why they are so green- they have green chlorophyll in
chloroplasts, organelles where photosynthesis occurs. Tens of thousands of years ago, leaves evolved to
become many things such as spines on a trunk or flowers that now give us the fruits we eat! Point to the
pitcher plant. What is it? (Take guesses.) A carnivorous plant, evolved to capture organisms! Of course,
the pitcher is an evolved leaf! How does the pitcher plant work? Discuss!! Carnivorous plants usually
occur in poor soils, which is why they have evolved to capture nutrients by trapping animals in these
“pitchers.” Carnivorous plants, like the pitcher plant and venus fly trip, get most of their nutrients from their
prey! Where do other plants get their nutrients? The soil! (Don’t confuse this with getting energy from the
sun.)
Plant anatomy – flowers
Point to a flower…what is this? Point to a less obvious flower (spathe and spadix of an Araceae, for
example, or an inflorescence or collection of flowers) to explain the many shapes and sizes of flowers.
Point to duckweed, which is the smallest flowering plant in the world (it is a few millimeters across and
grows on top of the water of the small pond near the station).
Plant anatomy – fruit
Right, and what does the flower turn into? The female parts of the flower turn into fruits!!!! Can you think of
any fruits? ….name fruits. Then name grains, which they probably will not realize are fruits. Tomato?
Fruit! Where do potatoes, carrots, and broccoli come from? These are instead a tuber (stem made for
storage), root, and flower buds, respectively!
Pollination and seed/fruit dispersal
What is required for the female flower to become a fruit? Fertilization! Male pollen, that “yellow stuff,”
needs to land on the female flower’s stigma. Point to the male parts (anthers) and female parts (style and
stigma) of the flowers. So what are the ways in which the pollen lands on the female flower? Wind, water,
bats, birds, insects. What is this transfer of pollen to the female parts called again? Pollination!! Why do
the insects and birds and bats, etc. visit the flowers? They gather nectar which is a sweet honey-like
reward OR pollen which can be sweet for them to eat OR sometimes male insects think that the flower is a
female partner and they mate with it! Talk about shapes of flowers and how they tend to match the mouth
parts of the pollinators. A long, tubular flower will likely be pollinated by the long tongue of a moth or the
long beak of a hummingbird, for example. So, then, this flower starts to grow into a fruit! Then what
happens? Fruits attract animals that eat the fruit but spread the seeds inside the fruit! Why is this good?
The seeds will grow into a juvenile (baby) plant.
DISCUSSION QUESTIONS:
Why are plants so uniquely important to humans, and all animals in general?
Plants are the only organisms (besides a few sparse bacteria) that create all of the energy that we have on
this Earth by capturing the sun’s energy through a process called photosynthesis.
What is the process of going from a flower to a juvenile (baby) plant?
The female parts of the flower are pollinated by pollen when either wind, water, birds, bats, or an insect
carries pollen to the stigma. The ovary, deep down inside of a flower, then begins to grow into a fruit, which
has seeds in it. An animal, wind, or water then disperses the fruit. The seeds inside the fruit grow into a
new plant.
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http://ysp.wustl.edu
Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
Who can explain to me the transfer of energy from the sun’s light to me clapping my hands? (Clap hands.)
How did I acquire energy to clap my hands right now!?
The sun’s energy is captured by the chloroplasts, generally in leaves, in a process called photosynthesis.
This allows the plant to survive. Then, a human either eats the plant directly or eats an animal which lives
on the plant. The human then has energy (originally captured by the plant) to clap his or her hands.
Why are some plants carnivorous? What are some examples of carnivorous plants and how do they
capture organisms?
Carnivorous plants usually occur in poor soils. In order to get nutrients, these plants have to capture
organisms and digest them with special enzymes. Both pitcher plants and Venus fly traps are carnivorous
plants which use pitcher-like cups or shutting leaves to capture their prey. These pitchers and the leaves
are modified, or evolved, versions of regular leaves.
4. STATION GROWTH FORMS
The purpose of this station is to describe and provide tropical examples of the various growth forms that
plants exhibit, as well as comparing how these different growth forms capture nutrients. Emphasis is placed
on three main facts: 1) that all plants compete for the same basic nutrients, 2) that these nutrients are
limited in the environment, and 3) that any feature or adaptation which enables a plant to get more nutrients
than another plant will help it survive and contribute more offspring to future generations due to natural
selection. The following is some helpful vocabulary.
Vocabulary –
1. Vascular plants (plants with vessels to transport water and nutrients):
a. Herb – plants without woody stems (complete 1 life cycle, then die and grow again from seed
in the next growing season)
i.
adaptation: fast life cycles make them good early successional plants (can colonize
fresh habitats, such as an open area that occurs after a tree falls)
b. Shrub – small woody plant (also succulents like cactus), generally < 3m in height
i.
adaptations: shorter height means they can put more energy into making additional
leaves and focus on catching sunlight that comes through the canopy; woody stems
offer protection from herbivores
c. Tree – large woody plant, generally > 3m in height, inhabits canopy and understory layers
i.
adaptation: grows tall above the other plants to get more sunlight
d. Vine – a plant (often herbaceous) with a climbing growth habit (can be for part or all of the
plant’s life cycle)
i.
adaptations: climbs other plants to reach sunlight, doesn’t need much space in the
understory; can have tendrils, thorns, or adventitious roots to enable climbing
e. Liana – a type of vine that is woody and rooted in the soil
i.
adaptations: generally the same as vines
f. Epiphyte – a plant that roots and perches non-parasitically upon another plant
i.
adaptations: grow on top of taller plants to get more sunlight; obtain water and
minerals via adventitious roots that cling to or enter bark of the host plant or in the
accumulated organic matter and litter at perch sites. These are also can have aerial
roots. Aerial roots may adhere to the host tree or grow downward from the canopy
ii.
can be epiphytic for all (true epiphytes) or part (hemiepiphytes) of their life cycle
1. strangler figs start as epiphytes, then send down many roots over time that
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Washington University School of Medicine
Climatron Tour at Missouri Botanical Garden
envelop and strangle the host tree; the viny exterior and hollow or
decomposing interior provide resources for many forms of life
2. Non-vascular plants (lack vessels for water/nutrient transport):
a. Often have an ‘encrusting’ habit (grow on tree trunks, rocks, the leaves of other plants, and
even animals, such as sloths)
b. E.g., lichens, mosses, liverworts, algae
DISCUSSION QUESTIONS:
● What is one BIG things plants can do that animals cannot do?
○ They can make their own food! (photosynthesis)
● What do plants need to be able to make their own food and grow? Do different types of plants need
different things, or do all plants need the same things?
○ Plants all need the same things! They need sunlight, water, nutrients from soil, and carbon
dioxide. Furthermore, these things (particularly the first 3) are limited in the environment
(there isn’t enough for everybody to have ALL that they want). SPACE is also a limited
resource in the tropics. Because resources are limited, competition is high.
○ High competition means that anything a plant can do to get more nutrients than other plants
will enable it to survive better and have more offspring than other plants. In other words,
nature will favor the individuals that are better competitors; we call this natural selection.
● Look at all the different plants around you. Do they all look the same--focus on overall shape, not the
specifics? Do they grow in the same ways? How do they differ?
○ As students make observations (trunks vs. no trunks, vines, tall vs. short, etc.), take the
opportunity to introduce key vocabulary and adaptations described above.
○ Growth form includes features such as position in stratification, type of branching, periodicity
(e.g., evergreen, deciduous), and leaf type.
○ In each type of ecosystem, we see many different growth forms (vocabulary above);
however, if we compare across ecosystems (e.g., temperate forests in the US vs. rainforests
in Costa Rica), then we would see the same types of growth forms in each ecosystem.