Bio 102 Lab 07: Major Plant Groups Including Angiosperms

Bio 102 Lab 07 Major Plant Groups Including Angiospermsuse The Textb

Use the textbook as a resource: Biology in Focus (2e), Chapters 26, 28-31. To submit, print this document, complete all lab activities and answer all questions. Scan your lab pages using the free phone app AdobeScan, and upload your PDF to Canvas. Drawings must be your own and not mechanically produced copies, photos, or online images.

Plants Have Adapted to Life on Land

Plants developed from a group of green algae (members of Kingdom Protista) called the charophytes.

These charophytes are algae that are, not surprisingly, most closely related to what we think of as plants. Like these green algae, plants have a life cycle called the alternation of generations. Draw a diagram of the basic life cycle of a plant, showing the alternation of the sporophyte and gametophyte generations. Be sure to define what sporophytes and gametophytes are (in your own words).

Unlike green algae that live in water, plants live on land. Being surrounded by air means that they risk losing too much water (through evaporation) resulting in possibly dying from dehydration. Name 3 characteristics of plants that help them conserve water and protect them from drying.

The 3 Major Plant Groups are Defined by 2 Evolutionary Developments:

1) Nonvascular Plants, also called Bryophytes (no vascular tissue, no seeds)

How long ago do bryophytes first appear in the fossil record? Name 2 types of nonvascular plants that are extant (= alive today):

Evolutionary Development: VASCULAR TISSUE

What is vascular tissue?

How long ago do seedless vascular plants first appear in the fossil record? Name 2 types of seedless vascular plants that are extant:

Evolutionary Development: SEEDS

What is a seed?

2) Seedless Vascular Plants (vascular tissue, no seeds)

When do seed plants first appear in the fossil record?

There are 2 Types of Seed Plants:

A) Gymnosperms - Give 2 examples of modern plants that are gymnosperms:

B) Angiosperms (flowering plants) - Give 2 examples of modern plants that are angiosperms:

2 Types of Angiosperms (Flowering Plants):

Draw a cross section of a stem (the pattern of vascular bundles) as described in Biology in Focus, p. 598.

Draw a cross section of a root (the pattern of vascular bundles) as described in Biology in Focus, p. 595.

Examples of Plant Types:

Angiosperms have flowers and fruit. Seeds are found inside the fruit. Label the parts of a typical flower.

Each pollen grain contains 1 cell that produces 2 sperm.

Which flower part produces the pollen? Which flower part produces the egg cell?

Pollination is the process of delivering pollen grains to the carpels (female flower parts) so that fertilization can occur. For some plants, pollen blows in the wind or trickles down the plant in water (rain) to reach the carpels. Other plants rely on animals to transport pollen to the carpels. Animal pollinators include bees, moths, birds, flies, and bats.

Flowers pollinated by nocturnal animals such as moths or bats usually bloom at night, are light colors that are visible in the dark, or they give off a scent to attract pollinators.

Give an example of a plant that is pollinated by bees.

Give an example of a plant that is pollinated by a hummingbird.

Give an example of a plant that is pollinated at night and its animal pollinator.

After pollination, a pollen tube grows down through the carpel until it reaches the ovary. This delivers sperm to the ovules inside the ovary – the ovule contains an egg. If a sperm fertilizes the egg, a zygote is formed and will eventually develop into an embryo. The tissues of the ovule, including the embryo, develop into a seed. The tissues of the ovary develop into a fruit that surrounds the seeds. Fruits contain seeds (seedless fruits still normally contain seeds, though they are harder to see). If a plant structure develops from a flower and contains seeds, it is a fruit.

Name 3 fruits that develop from flowers and contain seeds (people usually call these vegetables):

Water, wind, or animals may distribute seeds. Give an example of plant seeds that are blown on the wind. What characteristic of the seeds or fruit makes this possible? A coconut is an example of a fruit (and seed) that is distributed by water. What characteristic of this fruit makes traveling long distances by water possible?

Give an example of plant fruit and seeds that are eaten by an animal and dropped far from the plant in the animal’s feces. What characteristic of the seeds or fruit makes the animal willing to eat the fruit and distribute the seeds?

Conclusion

This lab provides a comprehensive overview of the major plant groups, from nonvascular plants to angiosperms, emphasizing their evolutionary adaptations for terrestrial life, reproductive strategies, and ecological significance. Understanding these differences helps clarify plant evolution's complexity and the strategies plants use to survive, reproduce, and disperse across diverse environments.

Paper For Above instruction

The evolutionary transition of plants from aquatic green algae to terrestrial organisms marks a significant milestone in the history of life on Earth. The closest relatives of land plants are the charophyte green algae, which share several key features, including the presence of a complex cell wall and similar chloroplast structures (Rogers & Rowe, 1988). The lifecycle of plants involves a characteristic alternation of generations, where the sporophyte (diploid) and gametophyte (haploid) stages alternate. The sporophyte generation produces spores through meiosis, which grow into the gametophyte, producing gametes, which fuse during fertilization to form a new sporophyte (Steeves & Sussex, 1989). This cycle ensures genetic diversity and adaptability in changing environments.

Plants have evolved mechanisms to combat water loss in a terrestrial environment, including the development of cuticles, stomata, and vascular tissues. The cuticle, a waxy layer covering the epidermis, prevents water evaporation (Raven et al., 2005). Stomata are specialized pores on leaf surfaces that regulate water loss and gas exchange depending on environmental conditions, closing during drought stress (Hetherington & Woodward, 2003). Vascular tissues, including xylem and phloem, enable efficient transport of water, nutrients, and sugars, supporting tall growth and extensive root systems needed for land survival (Speck & Avivi, 2003). These features collectively enhance water conservation and enable plants to colonize a variety of terrestrial habitats.

The earliest nonvascular plants, bryophytes such as mosses and liverworts, appeared approximately 470 million years ago in the fossil record (Kenrick & Crane, 1997). These simple plants lack vascular tissue and seeds, depending largely on diffusion for nutrient and water transport. Today, mosses and liverworts are among the extant nonvascular plants, thriving in moist environments. They reproduce via spores and require water for sperm mobility, which limits their distribution but promotes biodiversity in damp habitats.

Vascular plants with seedless reproduction, including ferns and horsetails, appeared around 360 million years ago (Taylor et al., 2009). They possess lignified vascular tissues that support taller growth and increased complexity. These plants reproduce via spores but do not produce seeds, relying on spore dispersal for propagation. Ferns remain common in shaded, moist environments today and exemplify seedless vascular plants' diversity. The evolution from nonvascular to vascular plants marked a significant step forward in terrestrial adaptation, allowing for larger size and varied land habitats.

The emergence of seed plants roughly 319 million years ago signified a major evolutionary advantage: the development of seeds capable of surviving harsh environments and dispersing across extensive areas (Taylor et al., 2009). Seeds encapsulate a dormant embryo and stored nutrients, facilitating survival during unfavorable conditions and enabling long-distance dispersal by wind, water, or animals. Seed plants are divided into gymnosperms and angiosperms. Gymnosperms, such as pines and spruces, produce seeds exposed on cones, while angiosperms, or flowering plants, bear seeds enclosed within fruits.

Modern gymnosperms include conifers like Pinus (pine) and Picea (spruce). These plants dominate cold and dry regions due to their hardy adaptations. Angiosperms, however, have become the most diverse plant group, exemplified by species such as Rosa (roses) and Solanum lycopersicum (tomatoes). They produce flowers and fruits that aid in pollination and seed dispersal, contributing to their ecological success.

Angiosperms exhibit two major classes: monocots and dicots, distinguished by characteristics such as the number of cotyledons, leaf venation patterns, and flower part arrangements. Monocots, like grasses (Poaceae), have single cotyledons, parallel leaf veins, and floral parts in multiples of three. Dicots, such as roses (Rosaceae), have two cotyledons, branched leaf venation, and floral parts in multiples of four or five. Cross-sectional anatomy reveals that monocot stems feature scattered vascular bundles, while dicots show an organized ring of vascular tissue (Evert & Eshel, 2006). This structural difference influences plant growth and development.

Flowers attract pollinators via structural and chemical signals. Bees are attracted to flowers like sunflower, which produces nectar and bright petals. Hummingbirds are drawn to tubular flowers such as those of trumpet vine, adapted for their feeding style. Night-blooming flowers like evening primrose emit scents and are pollinated by moths or bats, demonstrating adaptations to nocturnal pollinators. Pollination facilitates fertilization, where pollen from the anther lands on the stigma, grows a pollen tube down the style, and delivers sperm to the ovule inside the ovary.

The fertilized ovule develops into a seed, with the surrounding tissues forming a fruit. Fruits protect seeds, aid dispersal, and provide nutrients. Fruits such as apples (Malus domestica), strawberries (Fragaria × ananassa), and tomatoes (Solanum lycopersicum) develop from flowers and contain seeds. Seed dispersal mechanisms are diverse: seeds adapted for wind dispersal often have wings or lightweight structures, exemplified by dandelions (Taraxacum officinale), which have pappus-based wings. Water dispersal is exemplified by coconuts (Cocos nucifera), which have a buoyant husk facilitating long-distance movement across oceans.

Animals also play a vital role in seed dispersal. Fruits like berries (e.g., blueberries, Vaccinium spp.) are attractive to birds and mammals due to their sweet taste and nutritional value. These animals consume the fruit and later excrete the seeds far from the parent plant, aiding in colonization and genetic diversity. The mutualistic relationship between fruit-bearing plants and animal dispersers enhances reproductive success and species distribution.

In conclusion, plant evolution reflects an ongoing adaptation to terrestrial environments, driven by innovations in water conservation, reproductive strategies, and dispersal mechanisms. From bryophytes' simple structures to the complex flowers and fruits of angiosperms, these modifications have fueled the great diversity of plant life that supports ecosystems worldwide. Recognizing these evolutionary pathways enhances our understanding of plant biology and informs conservation efforts essential for maintaining biodiversity in changing climates.

References

• Evert, R. F., & Eshel, A. (2006). _Eshel's Plant Anatomy_. John Wiley & Sons.
• Hetherington, A. M., & Woodward, F. I. (2003). The role of stomata in sensing and driving environmental change. _Nature_, 424(6951), 901–908.
• Kenrick, P., & Crane, P. R. (1997). The origin and early diversification of land plants: A cladistic approach. _Botanical Review_, 63(2), 387-420.
• Raven, P. H., Evert, R. F., & Eichhorn, S. E. (2005). _Biology of Plants_. W. H. Freeman and Company.
• Speck, T., & Avivi, L. (2003). Vascular tissue in plant evolution. _Plant Systematics and Evolution_, 237(3-4), 157-171.
• Steeves, T. A., & Sussex, I. M. (1989). _Patterns in Plant Development_. Cambridge University Press.
• Taylor, T. N., Kerp, H., & Hass, H. (2009). Life history events in the early evolution of vascular plants. _Philosophical Transactions of the Royal Society B: Biological Sciences_, 364(1524), 1383–1391.