Biol 160: Lab 8
Name: __________________________
Exploring Plant Diversity
OBJECTIVES
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Become familiar with the diversity of plants.
Understand how each group of plants is defined by one or more evolved traits.
Observe the parts of the flower and their variations.
Observe fruits, how they are formed and how they are dispersed.
Observe conifer seed and pollen cones and pollen.
Become familiar with the alternation of generations.
Describe the life cycle of a typical fern and a typical angiosperm; distinguish between
the gametophyte and sporophyte generations.
Understand the changes in the alternation of generation that occurred over time,
moving from the bryophytes to the vascular plants.
General Procedures
This lab will be broken into three parts:
Part 1: Plant diversity scavenger hunt & comparison of plant diversity
Part 2: Flowers, fruits and cones lab
Part 3: Group activities reviewing alternation of generations and major plant traits
Part 1: The assignment - Plant diversity scavenger hunt at home or in-class.
In order to help you become more familiar with common members of the major plant groups
your instructor will ask you to collect plants either during class or at home. We will be collecting
specimens from each group. You will later use these specimens to help you visualize how the
alternation of generations have changed between the different plant groups. While collecting,
pay attention to the overall size of the plants you are collecting from, and in what environment
type you found them. Each lab group of 4-5 people should collect one specimen from each of
the following groups (you may decide how to divide and conquer):
• Bryophytes or non-vascular plants (mosses)
• Seedless vascular plants (ferns and horsetail)
• Gymnosperms (conifers or cone-bearing trees)
• Angiosperms (flowering plants)
Be prepared to explain which generation(s) you have collected!
Information to help you in your search:
A) Nonvascular plants “Bryophytes” (mosses)
The Bryophytes, or nonvascular plants, represent the earliest group of terrestrial
plants. The most familiar species in this group are the mosses. They do not have
vascular tissue (some mosses have simple tubular structures). Vascular tissues
serve two main purposes in plants: 1) as a transport system (tubes) for moving
water, sugars and minerals throughout the plant, and 2) it provides structural
support. Because Bryophytes do not have vascular tissue, they do not have true
leaves, stems and roots. The lack of vascular tissue limits the Bryophytes
morphologically and ecologically. Without vascular tissue to transport water, a
Bryophyte must be low lying or mat-like, so that all of its body can be in contact
Rev. 1/2009
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Biol 160: Lab 8
with the moist environment, and also be fairly thin in structure (only a few cells thick). Since
water is moving via osmosis through cells (a relatively slow process), the plant cannot be very
thick. Most Bryophytes need to live in moist environments, although they have many
adaptations for living in dryer environments. Additionally, the lack of vascular tissue means that
Bryophytes do not have the structural support to grow tall. Since the Bryophytes are all fairly
short plants, this leads to strong competition for sunlight and space.
B) Seedless vascular plants (ferns & horsetails)
Vascular tissue is composed of cells joined into tubes transporting water
and nutrients throughout the plant body. Xylem tissue is the watertransport tissue carrying water and minerals from the roots up the plant
body, and phloem tissue is the food-transport tissue carrying phloem
sap (food nutrients) from food sources (leaves or food storage organs)
to food sinks (growing non-photosynthetic structures or food storage
organs). The bodies of the vascular plants are divided into an aerial
shoot system (stems, leaves, and reproductive structures), and an
underground root system. True leaves, stems, and roots all contain true
vascular transport tissue.
The development of vascular tissue allowed the vascular plants to grow much taller than the
non-vascular plants for two reasons: 1) plants with vascular tissue no longer had to have most of
their body in contact with a moist environment, and 2) vascular tissue provided structural
strength within stems. Growing taller meant that they could intercept the light before lowgrowing plants could. This allowed the seedless vascular plants to become dominant during the
Carboniferous period. The most familiar seedless vascular plants are ferns. Both seedless
vascular plants and Bryophytes use spores to disperse (move the next generation further away
from the parent generation). Ferns have special spore producing structures, called sori, that are
typically visible underneath their leaves, which often look like rows of brown, green or whitish
dots.
C) Seed bearing vascular plants: Gymnosperms
Seed bearing vascular plants developed two structures that helped this group be successful in
dryer environments: 1) pollen, and 2) the seed. These structures are found in both gymnosperms
and angiosperms. Pollen is the male gametophyte (which will produce the sperm), wrapped in
a protective coating. Pollen allowed for the dispersal of the male gamete (sperm) over longer
distances and without the need for water. In Bryophytes and seedless vascular plants the sperm
must swim to the egg, so they require a moist environment. In seed bearing vascular plants, the
zygote develops into an embryo within the ovary. The embryo, its food supply and a seed coat
are packaged together by the plant as a seed. The seed can be released from the plant
to germinate in appropriate environmental conditions. Seeds provide several reproductive
advantages for these plants. First, they can increase dispersal of the next
diploid generation as the seed can be carried by the wind, water, or
another organism. Second, the food supply gives the developing embryo
an energy boost early in its life. With this energy boost, the embryo will
produce leaves that allow for photosynthesis and metabolic
independence. Third, the seed coat provides protection for the embryo
while it waits to germinate until conditions are suitable.
The most familiar gymnosperms are members of the conifer, or
“cone-bearing”, group which includes pine, fir, cedar and spruce trees.
Gymnosperm means “naked seed”. The seeds of gymnosperms are not
enclosed. In conifers they develop on the scales of the cone.
Gymnosperms can be quite tall and can be found both in moist and dry
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Biol 160: Lab 8
environments. Almost all the conifers are “evergreen”, holding their needle-like or scale-like
leaves year round. This allows for growth year round, although this growth is reduced in the
seasons of least sunlight. The reduced leaves are adapted to colder, drier climates with a thick
cuticle (waxy layer that prevents water loss). Commercially, most of our lumber and paper pulp
comes from the wood of conifers.
D) Seed bearing vascular plants: Angiosperms
The angiosperms are recognized as the “flowering plants.”
In addition to pollen and seeds, the angiosperms
developed two other distinctive traits: 1) flowers, and 2)
fruits. Flowers are made up of four main parts: 1) sepals, 2)
petals, 3) stamen, and 4) carpels. Many flowers have
been modified to attract insect, bird or mammal
pollinators. Modifications include bright colors, scents or
nectar rewards.
Angiosperm means “container seed”, and the seeds
are found within fruit. Fruit is a development of the
ovary tissue that surrounds the seed. Fruit evolved to aid in dispersal of the seeds. We will be
looking at types of fruits and dispersal mechanisms in Part II of this lab.
Part 2: Flowers, Fruits and Cones Lab
There will be several demonstration stations set up around the room. Go to each station and
examine the specimens. For each specimen answer the questions indicated at the station.
Make whatever drawings and notes necessary for you to remember the material and to be
able to answer the questions.
Station 1: Flowers to Fruits
This area contains a variety of specimens demonstrating the transition from flower to fruit.
After finishing with this station you should be familiar with:
• Identifying floral structures (sepals, petals, stamens, ovary, style, stigma) on developing and
mature fruits.
• Tell the difference between an inferior or superior ovary.
Station 2 A and B: Fruit Type & Dispersal
This area contains a variety of fruits and is divided into two parts: fruit type and fruit dispersal.
After finishing with this station you should be familiar with:
• Identifying different types of fruit.
• Determining how a fruit may be dispersed and describing the structural adaptations that
support your determination.
Station 3: Gymnosperm Reproduction
This area contains seed cones and pollen (staminate) cones of various conifer species.
After finishing with this station you should be familiar with:
• Determining the difference between a mature seed cone and a mature pollen cone.
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Biol 160: Lab 8
Part 3: Group Activity
A. Alternation of Generations.
Work in groups of 3-4 students to draw pictures of the following lifecycles and answer the
following questions. Use the descriptions above and the live plant materials to help you.
1. On a separate piece of paper make a sketch of the lifecycle of a fern (alternation of
generations). Place the following labels on the sketch: sporophyte, gametophyte, gametes,
spores, mitosis, meiosis, diploid, haploid, fertilization, zygote.
2. On a separate piece of paper make a sketch of the lifecycle of an angiosperm (alternation
of generations). Place the following labels on the sketch: sporophyte, gametophyte, gametes,
spores, mitosis, meiosis, diploid, haploid, fertilization, zygote, stamens, anther, carpel, ovary,
seed, flower, fruit.
3. What are the major changes in alternation of generation that occurred over the evolution of
plants? Why was each change important?
4. What is the difference between a spore and a seed?
5. Which groups of plants use spores in dispersal? Which use seeds?
6. What benefits could be gained by using seeds as the unit of dispersal rather than spores?
7. What is fruit and how was it important in the evolution of plants?
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