Intro to Botany

Setting the Stage
• All living beings have all of the following characteristics; if even one is missing, the material is not alive:
−Metabolism involving the exchange of energy and matter with the environment
−Nonrandom organization
−Growth
−A system of heredity and reproduction
−A capacity to respond to the environment such that metabolism is not adversely affected

What is botany?
• Biology is the science of life or living matter in all its forms and phenomena, especially with reference to origin, growth, reproduction, structure, and behavior. (Dictionary.com)
• Botany is a subdiscipline of biology and is commonly defined as the scientific study of plants.

What is a plant?
• Most have green leaves, stems, roots, and flowers, though there are exceptions.
- Conifers (gymnosperms) don’t produce flowers.
- Mosses lack true leaves, stems, and roots and neither mosses or ferns produce flowers.

• Fungi were once considered plants but are now excluded.
• Green algae are problematic.
- Similar to plants at the cellular and biochemical level
- But share more characteristics with other algae

What do we study plants? Why does it matter?
• Plants changed the climate of Earth in ways that we can now live on it.
• Plants also produce the oxygen we breathe and the food we eat.
• We get cloth, paper, lumber, medicines and chemicals from plants, and plants are important to us for their aesthetic
qualities.

Using Concepts to Understand Plants
There are a few fundamental concepts that will make plant biology more easily understood.
1.Plant metabolism is based on the principles of chemistry and physics.
– All the principles you learn in your chemistry or physics classes are completely valid for plants.

2. Plants must have a means of storing and using information.
– Genes are the primary means of storing this information.

3. Plants reproduce, passing their genes and information on to their descendants.
– Seeds contain information from their parents.

4. Genes, and the information they contain, can change.
– Plants copy genes during reproduction.
– These changes cause differences in offspring.
– Over time, a gradual evolution occurs.

5. Plants must survive in their own environment.
– They must be adapted to their environment.
– Plants more suited to their environment reproduce more successfully and produce more offspring.
– The presence of other organisms may be detrimental, beneficial, or neutral.

6. Plants are highly integrated organisms.
– The structure and metabolism of one part tend to impact the rest of the plant.
– An adaptation in one area is often balanced by changes in another.

7. An individual plant is the temporary result of the interaction of genes and environment.
– The way a plant interacts with its environment is guided by genetic information that has slowly evolved over thousands of years.
– The genetic pool of the species exists beyond the phenotype represented by a single specimen.

8. Plants do not have purpose or decision-making capacity.
– Anthropomorphism and teleology should be avoided.
• Anthropomorphism: applying human characteristics to non-human organisms or things
• Teleology: the assumption that processes or structures have a purpose

Origin and Evolution of Plants
• Organisms were originally simple and increased in complexity through evolution by natural selection.

Natural Selection
• Organisms reproduce and have non-identical offspring whose features pass to more offspring.
• Offspring with features that are well-adapted to the environment reproduce more

• New features arise periodically by mutations.
• Natural selection determines whether new features are eliminated or passed on to future generations.
• Evolution by natural selection is a model consistent with:
−Observations of natural organisms
−Experiments
−Theoretical considerations

Origin of Plants
• Life on Earth began about 3.5 billion years ago with prokaryotes (bacteria and archaeans).
−Photosynthesis arose 2.8 billion years ago in a cyanobacterium.
• Organelles evolved followed by division of labor and specialization.
−DNA became located in its own organelle, the cell nucleus.
−Development of organelles was followed by division of labor and specialization.
−Eukaryotes have nuclei (plants, fungi, animals, algae).

• Eukaryotes diversified, some gaining mitochondria and some gaining chloroplasts (endosymbiotic theory).
−Those with mitochondria evolved into protozoans, fungi, and animals.
−Those with mitochondria and chloroplasts evolved into plants and algae.
• All organisms fit into three large groups called domains: Bacteria, Archaea, and Eukarya.

• Early plants resembled green algae.
−They lost many algal features and gained features suitable for life on land through natural selection.
• Not all organisms evolve at the same rate.
−Features that seem relatively unchanged are relictual features or plesiomorphic features.

• Flowering plants evolved 100–120 million years ago.
−Several features characteristic of this group evolved at this time, including:
• Flowers
• Simple, flat, broad leaves
• Wood

• Some modern groups have derived (or apomorphic) features.
−These are features that evolved from an ancestral feature.
−Modern secondary chemical compounds are an examples of derived features.

Diversity of Plant Adaptations
• Over 297,000 plant species exist today; wide diversity of adaptation is important.
• For any aspect of the environment, many types of adaptation are possible.
−There is no single, perfect adaptation.
−There are alternative adaptations.
−There are ways of coping with different environments and the multitude of factors within them.