Lecture 16- Plant diversity- Spring 2026

Flowers produce bright colors, patterns, and enticing fragrances to attract pollinators.
Researchers at Bristol’s School of Biological Sciences, led by Professor Daniel Robert, made a significant discovery about floral communication:
- Flowers emit patterns of electrical signals that convey information to insect pollinators.
- These electrical signals work alongside the other attractive signals of the flower, enhancing floral advertising power.
- Bumblebees have the capability to detect and distinguish between these electrical fields, indicating an advanced form of communication and attraction.

Scientists have recently identified a marine fungus capable of infecting and killing toxic algae responsible for harmful blooms.
This fungus, named Algophthora mediterranea, infects algae species like Ostreopsis ovata, which produces harmful toxins affecting human health by irritating lungs, skin, and eyes during coastal blooms.
Key characteristics of Algophthora mediterranea:
- It can infect multiple algae species.
- It has the ability to survive on pollen, indicating a higher adaptability than most known marine parasites.

With the increasing challenge of drug-resistant bacteria, scientists are seeking new antibiotic targets.
Recent studies unveiled how viruses that infect bacteria can shut down a vital protein known as MurJ, which is essential for bacterial cell wall construction.
Notably, various viruses have independently evolved different proteins that inhibit MurJ in the same manner, positioning it as a promising target for new antibiotics.

The three domains of life delineate the earliest branches of evolutionary history:
- Bacteria
- Archaea
- Eukarya, which encompasses animals, fungi, plants, and protists.
Kingdom Platoe (kingdom of plants) saw the emergence of four major groups that evolved from algae:
- Bryophytes (nonvascular)
- Ferns (seedless vascular)
- Gymnosperms (naked-seed plants)
- Angiosperms (flowering plants)

Three pivotal adaptations are crucial for distinguishing these four major plant groups:
1. Vascularity – The development of vascular tissues for nutrient and water transport.
2. Seeds – Formation of seeds for reproduction and protection of the embryo.
3. Flowers – Development of flowers to enhance reproductive success.

Timeline of plant evolution concerning key adaptations:
- Origin of first terrestrial adaptations – Approximately 475 million years ago (mya)
- Origin of vascular tissue – Approximately 425 mya
- Origin of seeds – Approximately 360 mya
- Origin of flowers – Approximately 140 mya
Charophytes represent a lineage of green algae and are considered modern-day relatives of early plant ancestors.
Plant groups can be classified based on vascularity and reproductive mechanisms:
- Nonvascular: Bryophytes
- Vascular: Ferns (seedless), Gymnosperms (naked seeds), Angiosperms (flowering plants)

Key adaptations that allow plants to thrive on land:
- Waxy Cuticle – This layer reduces water loss.
- Stomata – Regulate gas exchange, allowing plants to manage water while taking in carbon dioxide for photosynthesis.
- Vascular Tissue – Composed of specialized conducting cells called vessels, which transport water and nutrients throughout the plant. These vessels typically contain lignin, a stiffening substance that provides structural support, allowing plants to grow taller.

Known as “simple” plants, often grouped as mosses.
- Lack true roots, leaves, and stems.
- Absence of vascular tissue means they rely on diffusion for nutrient transport.
- They cannot achieve tall growth and require water for sperm motility to fertilize eggs.
Among the main types are liverworts and mosses.

Include plants that produce spores instead of seeds, with approximately 12,000 known species.
- Sperm are motile and require water for reproduction.
Examples include:
- Club moss
- Horsetail
- Deer fern

Non-flowering seed plants that evolved before angiosperms.
- The largest group comprises conifers, including pines, firs, spruces, hemlocks, and cypresses.
- They remain green throughout the year, generally referred to as evergreens.
- Their leaves are modified into thin needles protected by a waterproof layer, minimizing evaporation.
- They produce an antifreeze in their sap and emit characteristic aromas.

Flowering seed plants dominant on Earth for more than 100 million years.
- Comprising over 230,000 species, these plants are critical for ecosystems and agriculture.
- Characterized by production of flowers, fruits, and broad leaves, they make up a significant proportion (approximately 90%) of the world’s plant species.

Flowers perform the essential role of attracting pollinators:
- They are sites for the formation of male and female gametes.
- Insects consume pollen as a protein source while assisting in pollen transport between plants, which enhances genetic diversity.
- Eliminate reliance solely on wind for pollination.

Pollinators are vital for agriculture and contribute substantially to economies:
- Honey bees are responsible for the pollination of at least 90 commercially grown crops in North America.
- Globally, about 87 out of 115 leading food crops depend on animal pollinators, accounting for roughly 35% of global food production.
- Pollination services are valued at over 24 billion dollars in the U.S. economy, with native insect pollinators contributing more than 9 billion dollars in crop benefits in 2009.

The ovary surrounding seeds matures into a fruit, which serves several functions:
- Provides vital calories for animals which eat the fruit.
- Animals effectively disperse seeds through their waste, facilitating plant propagation to new locations.

Coevolution examples:
- Birds and Capsicum peppers:
- Capsaicin, a chemical found in chili plants, deters most mammals but does not affect birds, which disperse the seeds after consuming the peppers.
- Research indicates that passage through bird guts enhances seed germination rates.
Other notable adaptations include:
- Wind Dispersal – Dandelions effectively utilize wind for seed distribution.
- Viviparous Mangroves – Some mangrove species, such as the red mangrove, have seeds that germinate while still attached to the parent tree, producing propagules capable of photosynthesis.
- Animal Transportation – Seeds that attach to animals for transportation contribute to their dispersal.

Plants are significant resources for medicinal purposes:
- More than 70,000 plant species are utilized for medicinal benefits.
- Approximately 50% of drugs prescribed in the United States have origins in plant compounds.