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Plant Diversity - part 1
Name:_________________________
OBJECTIVES:
• 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 seeds cones.
General Procedures
This lab will be broken into two parts:
Part 1: Explore plant diversity & comparison of plant diversity
Part 2: Flowers, fruits and cones lab
Part 1: The assignment - Plant diversity
*On the last page, draw one example from each group, label two similarities between all groups, and one
difference!
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 serves 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 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 water-transport 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 low-growing 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. Spores are usually haploid and unicellular and are produced by meiosis in the
sporangium by the sporophyte. Once conditions are favorable, the spore can develop into a new organism using
mitotic division, producing a multicellular gametophyte, which eventually goes on to produce gametes. Two
gametes fuse to create a new sporophyte. This cycle is known as alternation of generations, but a better term is
"biological life cycle", as there may be more than one phase and so it cannot be a direct alternation. Haploid
spores produced by mitosis (known as mitospores) are used by many fungi for asexual reproduction.
Spores are the units of asexual reproduction, because a single spore develops into a new organism. By contrast,
gametes are the units of sexual reproduction, as two gametes need to fuse to create a new organism.
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 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
Examine the specimens on the stations. 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 section you should be familiar with:
• Identifying floral structures (sepals, petals, stamens, ovary, style, stigma) on developing and mature fruits.
• Use the drawing in your lab book to label the structures on your drawing, note which ones are male and which
ones are female.
Basic Flower Drawing
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 able to:
• Identify different types of fruit.
•For each type of see that you draw, determine how a fruit may be dispersed and describing the structural
adaptations that support your determination.
Fleshy Fruit
Simple Fruit
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:
• Where do the seeds hide in the cone
• What advantage is there to having a cone?
.
White Pine (Pinus strobus) Cone
1. What is the difference between a spore and a seed?
2. Which groups of plants use spores in dispersal? Which use seeds?
3 What benefits could be gained by using seeds as the unit of dispersal rather than spores?
4. What is fruit and how could it have been important in the evolution of plants?
5. Where are the seeds in a cone?
Plant diversity Drawings