BIOL 1010 | Chapter 17

Characteristics of charophytes

Photosynthetic, multicellular algae; lack rigid support tissues; anchored by a holdfast; absorb minerals/CO₂ directly from water; reproduce with flagellated sperm swimming to eggs.

Plants had to evolve to survive and reproduce on dry land - what did they develop?

They developed waxy cuticles, stomata, vascular tissue, lignin-reinforced cell walls, roots, apical meristems, gametangia, pollen, seeds, and dependent embryos.

Where did algal ancestors live, and what adaptations were needed?

• Lived in shallow waters (lake fringes, salt marshes) that periodically dried.

• Adaptations needed: ability to resist drying, structural support outside water, mechanisms for gas exchange, reproduction without reliance on water.

• Modern resemblance: Coleochaete (disk-like colonies growing at lake edges).

When did first land plants appear in fossil record?

About 470 million years ago.

Early advantages of living on land.

Unlimited sunlight, abundant atmospheric CO₂, few pathogens and herbivores initially.

Challenges faced by early land plants.

Be able to maintain moisture inside cells, support body in non-buoyant medium, reproducing without water, anchoring in soil, and connecting underground/aboveground resource systems.

How do modern algae differ from land plants?

• Algae lack vascular tissue, rigid supportive tissues, and stomata.

• They absorb nutrients across their body surface, rely on water for reproduction/dispersal.

• Land plants have roots, stems, leaves, vascular tissue, lignin support, stomata, and protective reproductive structures.

How do plants maintain moisture?

With a waxy cuticle covering surfaces and stomata for controlled gas exchange.

What is the purpose of stomata?

To allow CO₂ in and O₂ out for photosynthesis, while reducing water loss by closing when conditions are dry.

What minerals and nutrients are gained form air and soil?

• From soil: water and minerals (e.g., nitrogen, phosphorus, potassium).

• From air: CO₂ (for photosynthesis) and O₂ (for respiration).

What organs are used for resource acquisition?

• Roots → water and minerals.

• Stems → structural support and transport.

• Leaves → CO₂ and sunlight for photosynthesis.

How do plants connect subterranean and aerial parts?

with vascular tissue (xylem and phloem)

Differentiate xylem vs. phloem

• Xylem → dead, lignin-reinforced cells; transports water/minerals upward.

• Phloem → living cells; transports sugars throughout plant body.

why are non-vascular plants short?

They lack lignin-reinforced tissues and efficient vascular transport systems, so they cannot support tall growth or transport water/nutrients far.

how do vascular plants support their bodies?

With lignin in xylem and other tissues, which provides rigidity and strength against gravity.

how does reproduction of mosses and ferns work?

• Use gametangia to produce eggs and sperm.

• Require moist environments since sperm must swim to eggs.

• Disperse offspring via spores produced in sporangia.

how does reproduction of pines and flowering plants work?

• Use pollen grains to transport sperm, eliminating need for water.

• Produce seeds containing embryos, food supply, and protective coats.

• Dispersal occurs via wind or animals.

Describe the alternating haploid/diploid life cycle of plants

• Haploid gametophyte → produces gametes.

• Fertilization → diploid zygote.

• Zygote develops into diploid sporophyte.

• Sporophyte produces haploid spores in sporangia.

• Spores grow into gametophytes, continuing the cycle.

What is the difference between a seed and a spore?

• Spore = single haploid cell, minimal resources, relies on environment.

• Seed = diploid embryo with stored food and protective coat, more resilient and capable of long-distance dispersal.

Describe the steps in the evolution of modern plants.

1. Origin of plants from algal ancestors (~470 mya).

2. Early diversification into nonvascular plants (bryophytes).

3. Evolution of vascular plants with lignified tissues (~425 mya).

4. Diversification into seedless vascular plants (lycophytes and monilophytes).

5. Evolution of seed plants (~360 mya), including gymnosperms.

6. Appearance of angiosperms with flowers and fruit (~140 mya).

What are some characteristics of bryophytes?

Lack true roots and leaves, no lignified support tissues, depend on dense mats for structure, reproduce with flagellated sperm, retain embryos on the parent, and require moist environments for reproduction.

What are some examples of early nonvascular plants?

Mosses, liverworts, and hornworts.

how do mosses hold themselves upright?

By growing in dense mats; the tightly packed plants support each other like a crowd.

how do bryophyte sperm move?

flagellated sperm swim through a film of water (rain or dew) to reach eggs.

when did vascular plants evolve?

About 425 million years ago.

what are some characteristics of vascular plants?

Lignin-hardened vascular tissues (xylem and phloem), true roots and leaves, ability to grow tall, and efficient transport of water, minerals, and sugars.

where do ferns live?

Most common in temperate forests, but most diverse in tropical regions; some grow as tall tree ferns.

how do ferns and club mosses disperse offspring?

Through air-dispersed spores produced in sporangia.

when did vascular plants with seeds evolve?

About 360 million years ago.

why are seeds key adaptations?

They protect embryos with a coat, provide a food supply, allow survival in harsh conditions, and enable wide dispersal across terrestrial habitats

why are gymnosperm seeds naked?

Because they are not enclosed within specialized protective chambers (unlike angiosperm seeds, which are enclosed in fruits).

what are some types of gymnosperms?

Conifers (pine, spruce, fir), cycads, ginkgo, and Ephedra.

what are some types of angiosperms?

flowering plants such as grasses, shrubs, and flowering trees; the most diverse plant lineage.

what is a flower?

A reproductive structure of angiosperms that produces gametes and seeds within protective chambers, often adapted for pollination by animals or wind.

what are the 4 key adaptations for land plants?

1. Dependent embryos (all plants).

2. Lignified vascular tissue (vascular plants).

3. Seeds (gymnosperms and angiosperms).

4. Flowers (angiosperms).

In humans, what cells are diploid and what cells are haploid?

• Diploid: Almost all human cells (somatic cells) with two sets of chromosomes.

• Haploid: Only gametes (sperm and eggs).

What is an alternation of generation?

A plant life cycle that alternates between two multicellular stages: a haploid gametophyte (produces gametes) and a diploid sporophyte (produces spores). Each generation gives rise to the other.

What stage of the life cycle is the larger, more obvious one in nonvascular plants?

The gametophyte is dominant in nonvascular plants like mosses.

What stage of the life cycle dominates the vascular plants?

The sporophyte is dominant in vascular plants like ferns.

What stage of the life cycle dominates for seed plants?

The sporophyte dominates seed plants (gymnosperms and angiosperms).

Explain in detail the life cycle of a plant:

1. The diploid sporophyte produces haploid spores by meiosis in sporangia.

2. Spores disperse and grow into multicellular haploid gametophytes.

3. Gametophytes produce gametes (sperm and eggs) by mitosis in gametangia.

4. Fertilization occurs when sperm and egg unite, forming a diploid zygote.

5. The zygote develops into a new multicellular sporophyte, completing the cycle.

When was the Carboniferous period and where did seedless vascular plants live? What conditions existed?

• The Carboniferous period lasted from about 359–299 million years ago.

• Seedless vascular plants (lycophytes and monilophytes) grew in vast swampy forests in low-lying wetlands near the equator of what are now Eurasia and North America.

• Conditions: warm, humid, and wet climates that supported dense, lush vegetation.

What organisms lived in these swamp forests? Characteristics?

• Giant lycophytes and tree ferns (up to 12 stories tall, >2 m thick).

• Huge insects like dragonflies with 1 m wingspans.

• Amphibians and early reptiles adapting to terrestrial habitats.

• These organisms were adapted to moist, swampy environments and included some of the largest plants and arthropods to ever live.

What effect did photosynthesis have on the atmosphere and environment? How did this affect climate change?

• Photosynthesis fixed large amounts of atmospheric CO₂ into organic molecules.

• This drastically lowered CO₂ levels, reducing greenhouse gases and causing global cooling.

How was organic matter converted into coal?

1. Plants died and accumulated in stagnant swamps, forming peat.

2. Peat was buried under seawater and marine sediments.

3. Over millions of years, pressure and heat compressed peat into coal.

What is the origin of coal, oil, and natural gas?

• Coal: From ancient land plants (peat deposits).

• Oil: From remains of marine microorganisms buried under sediments.

• Natural gas: From marine organisms, often alongside oil, formed under higher heat and pressure.

Why does burning fossil fuels cause climate warming?

• Burning fossil fuels releases large amounts of CO₂ and other greenhouse gases back into the atmosphere.

• These gases trap heat (greenhouse effect), causing global warming.

In the Carboniferous period, what effect did global cooling have, and how did this allow seed plants to diversify?

• Cooling led to glacier formation, drier climates, and the collapse of swamp forests.

• Seedless plants, which required moist habitats for reproduction, declined.

• Seed plants, with protective seeds and wind-dispersed pollen, could reproduce without water and therefore thrived and diversified in the new drier environments.

Pollen carry sperm-producing cells through the air.

Unlike seedless plants that rely on swimming sperm in water, seed plants use pollen grains to transport sperm-producing cells via air or animals, enabling reproduction in dry environments.

Seedless plants make haploid spores that must survive as gametophytes.

These spores must grow independently into gametophytes before producing gametes, making them more vulnerable.

Seed plants produce diploid sporophytes as the next generation.

Instead of haploid spores, seed plants disperse seeds that contain a diploid embryo, already prepared to grow into the sporophyte stage.

What are all the reproductive stages of a seed plant?

Spore → gametophyte → gametes (egg and sperm) → fertilization → zygote → embryo → seed → sporophyte.

What is the structure and purpose of a cone in gymnosperms?

Cones are modified shoots bearing scales with sporangia. They house all reproductive stages (spores, gametophytes, gametes, zygotes, embryos) and protect them within the parent sporophyte.

Differentiate between male and female reproductive structures.

• Male cones: Produce haploid spores that develop into pollen grains (male gametophytes), which contain sperm nuclei.

• Female cones: Produce haploid spores that develop into ovules (female gametophytes), which produce eggs and later develop into seeds.

What happens when a pollen grain lands on a compatible female structure?

Pollination occurs → the pollen grain undergoes mitosis to produce a sperm nucleus → a pollen tube grows into the ovule → the sperm nucleus is released → fertilization follows.

Differentiate between pollination and fertilization:

• Pollination = transfer of pollen to a female structure.

• Fertilization = actual fusion of sperm and egg nuclei inside the ovule.

When a seed is formed, what does it contain and what is the advantage?

• A seed contains a diploid embryo, a stored food supply, and a protective seed coat.

• Advantage: it shields the embryo, provides nourishment, and allows wide dispersal and survival in harsh conditions.

Flowers are the site of pollination and fertilization and hold male and female sporangia and gametophytes, explain this.

Flowers function as reproductive centers, with stamens producing pollen (male gametophytes) and carpels housing ovules (female gametophytes). They facilitate pollination, fertilization, and the development of seeds.

what is the purpose and function of floral structures?

• Receptacle: Foundation where all flower parts attach.

• Sepals: Protect unopened buds.

• Petals: Attract pollinators through colour, shape, or scent.

• Stamen: Produces pollen (male gametophytes).

• Anther: Produces and releases pollen grains.

• Carpel: Female reproductive structure where fertilization and seed development occur.

• Ovary: Contains ovules, which develop into seeds after fertilization; later matures into a fruit.

As an ovary matures, what does it become?

The ovary develops into a fruit, which encloses and helps disperse seeds.

Describe in detail the life cycle of angiosperms.

1. Meiosis in anthers → produces haploid spores that undergo mitosis to form male gametophytes (pollen grains).

2. Meiosis in ovules → produces haploid spores that undergo mitosis to form the female gametophyte, one cell becoming the egg.

3. Pollination → pollen grain lands on a compatible stigma, carried by wind or animals.

4. Fertilization → pollen tube grows into the ovule; sperm nucleus travels down the tube and fuses with the egg to form a zygote (diploid).

5. Seed formation → each fertilized ovule develops into a seed, which contains an embryo (sporophyte), food supply, and protective seed coat.

6. Fruit development → ovary wall thickens around the seeds, forming a fruit that aids seed protection and dispersal.

7. Germination → when conditions are right, the seed sprouts; the embryo uses stored food until it can photosynthesize, eventually developing into a mature sporophyte.

   • The cycle then repeats with meiosis in the sporophyte to produce new gametophytes.

explain the process of meiosis and mitosis in plants.

• Meiosis: Reduces chromosome number by half, producing haploid spores from diploid sporophytes. Essential for genetic diversity.

• Mitosis: Cell division that maintains chromosome number; in plants, it allows haploid spores to grow into gametophytes and helps the diploid zygote grow into a multicellular sporophyte.

What adaptations do angiosperms have that give them an advantage over other plants?

• Flowers: Attract animal pollinators, which move pollen more efficiently and reliably than wind, increasing reproductive success.

• Rapid reproduction: Fertilization can occur within ~12 hours of pollination; seeds can form in days to weeks (much faster than gymnosperms, which can take years).

• Fruits: Protect seeds and aid in dispersal by wind, water, or animals.

• Seed packaging: Embryo with food supply + protective seed coat allows survival in harsh environments and long dormancy periods.

how do fruits help with the dispersal of wind-dispersed fruits? Give one example.

• Some fruits have lightweight, parachute- or wing-like structures that catch air currents.

• Example: A dandelion’s fruit has fine, hair-like extensions that let the seed float far from the parent plant, reducing competition.

how do fruits help with the dispersal of fruit that cling to animals? Give one example.

• Fruits may develop hooks or spines that latch onto fur, feathers, or clothing.

• Example: Cocklebur fruits can be carried for miles before detaching, spreading seeds widely.

how do fruits help with the dispersal of fruit that’s fleshy edible? Give one example.

• Brightly coloured, sweet, and nutritious when ripe, attracting animals to eat them.

• Seeds often have tough coats that survive digestion, so animals deposit them elsewhere in feces—sometimes with fertilizer.

• Example: Birds like catbirds eat berries and spread seeds long distances.

• These diverse dispersal strategies are a major reason angiosperms have been so successful across nearly all habitats.

What fruits are staples in the human diet all over the world?

• The main staple fruits are grains, which are actually dry fruits of grasses.

• Examples: corn, rice, wheat, barley, oats, and other cereals.

• These provide the bulk of calories for most people and their domesticated animals.

Give examples of fleshy fruits we eat

• Common fleshy fruits include: apples, cherries, oranges, tomatoes, squash, cucumbers, grapes, peaches, and melons.

• Botanically, some foods we call “vegetables” (like cucumbers and tomatoes) are actually fruits because they contain seeds.

Many spices also come from angiosperms even if we aren't eating the actual fruit

• Examples of spice plants: nutmeg, cinnamon, cumin, cloves, ginger, and licorice.

• These come from different plant parts (bark, roots, seeds, fruits), but all are from angiosperms.

What fruit was incredibly valuable in medieval Europe and how is it prepared for our use?

• Black pepper was highly prized in medieval Europe.

• The fruits (peppercorns) are harvested before ripening, dried, and sold whole or ground into powder.

• Peppercorns were so valuable they were used as currency, tax payments, dowries, and inheritances.

What was the driving purpose of the "Age of Exploration"?

• The search for a sea route to India and Southeast Asia to obtain pepper and other precious spices.

• This economic drive for spice trade significantly shaped European expansion, colonization, and global history.

How do the Red Maple tree and Columbine plants allocate their energy differently to ensure pollination occurs?

• Red maple: invests energy in producing massive amounts of pollen that are dispersed by the wind. This method is less reliable, so the plant compensates by sheer quantity.

• Columbine: invests energy in producing large, colourful, fragrant flowers that attract animal pollinators. This costs more energy, but ensures more precise pollen transfer between flowers of the same species.

What animals serve as pollinators?

• About 90% of angiosperms use animal pollinators.

• Common pollinators include: bees, butterflies, moths, beetles, birds, and bats.

What does a flower provide to a pollinator?

• Flowers provide nectar, a high-energy sugary fluid that serves as food for pollinators.

• Some also provide pollen itself as a protein source.

What aspects of a flower are specific types of pollinators drawn to?

• Birds → bright red/orange flowers, little to no scent.

• Beetles → strong fruity odours, less interested in colour.

• Bees → flowers with colour patterns and nectar guides, including UV markings invisible to humans.

• Bats and moths → large, light-coloured, highly scented flowers visible/smellable at night.

• Carrion flies and beetles → flowers that smell like rotting flesh, mimicking food sources.

What adaptations do flowers often have to improve pollen transfer and reproductive success?

• Nectar placement forces pollinators to brush against stamens and stigmas.

• Specialized shapes (like columbine spurs) only allow certain pollinators to access nectar, ensuring pollen is carried to the right species.

• Timing of flower opening (day vs. night) matches pollinator activity.

• Guides and scents direct pollinators to pollen/nectar efficiently.

How do extraction techniques ensure a pollinator visits the same species of plants instead of traveling in a more random manner?

• Pollinators (especially insects) must learn how to extract nectar from each type of flower.

• They are more efficient if they keep visiting the same flower species immediately after learning.

• This increases pollinator fidelity and improves cross-pollination success for the plant.

What is the purpose of caffeine in plants in terms of reproductive success?

• Some flowers add caffeine to their nectar, which enhances memory in pollinators like honeybees.

• This makes pollinators more likely to remember and return to the same flower species, improving pollination accuracy and success.

Early humans ate a variety of plants depending on the season. Explain this:

Before agriculture, humans were hunter-gatherers who relied on any edible plants available in their environment. Their diet shifted throughout the year, depending on seasonal growth and availability, which provided natural diversity in their food sources.

During the development of agriculture, what did humans select for artificially in crop plants?

Humans selected for plants that were the tastiest, easiest to cultivate, and most productive. Over time, through repeated planting and breeding, they emphasized traits such as larger seeds or fruits, reduced bitterness or toxins, and higher yields.

How has agriculture decreased the variety of plants that are used for food?

Agriculture narrowed the diversity of plants by focusing on just a few high-yield, desirable species. Modern breeding techniques have reduced genetic variation further, leading to global dependence on just a handful of crops—primarily rice, wheat, corn, and soybeans—while many other edible species are neglected.

How has agriculture changed the landscape?

Agriculture reshaped landscapes by clear-cutting and burning forests to make farmland, and later through deforestation on a massive scale for crop expansion. Unsustainable practices have degraded large areas of cropland, while roads and development fragment habitats, reducing their ability to support diverse plant species.

Examples of species that may be suitable for domestication and production to add to plant diversity

• Many nutritious wild plants show promise, including fruits such as chocolate berries, gingerbread plums, monkey oranges, marula, and Natal plums.

• Certain African grains are also strong candidates, as they tolerate heat, drought, infertile soils, and can even grow on sand dunes with minimal rainfall. These resilient species could help diversify agriculture, especially in marginal lands.

What genes or traits would be ideal to add to crop plants so that they can thrive in less ideal conditions?

• Useful traits include:

  • Salt tolerance (for growth in saline soils)

  • Pest resistance (reducing crop losses)

  • Heat and drought tolerance (allowing survival in extreme climates)

• Such genes often exist in the wild relatives of current crops, making conservation of those species critical.

How are we causing the loss of natural plant diversity in the world?

• Human activities such as deforestation, logging, mining, and pollution destroy habitats.

• Road building and land fragmentation break ecosystems into smaller patches too limited to support full species diversity.

• As habitats disappear, so do potential new crops and wild relatives of existing crops, which reduces the pool of genetic diversity available for agriculture.

In what way will the loss of diversity affect the world’s future supply of food?

• Losing plant diversity reduces the availability of new species for domestication and wild relatives that provide useful genes (for pest resistance, climate tolerance, etc.).

• This makes global agriculture more vulnerable to pests, diseases, and environmental changes, since the limited number of crops we depend on may not adapt quickly enough. Ultimately, reduced diversity threatens long-term food security for the world’s population.

Give examples of different fungi you may see in your everyday life.

Common fungi include mushrooms sprouting in soil or lawns, bracket fungi attached to trees, and molds that grow on bread, fruit, or other leftover food. Each of these has different visible structures, but they all absorb nutrients in the same way.

Explain the process of absorption for nutrient acquisition.

Fungi secrete powerful enzymes into their surroundings, which break down complex macromolecules (like starch, cellulose, or lignin) into smaller monomers (like glucose). These small molecules are then absorbed through the hyphae into the fungal cells, allowing the fungus to feed without ingesting material directly.

Fungi are essential decomposers in most ecosystems.

By breaking down tough plant materials such as cellulose and lignin, fungi recycle nutrients back into the soil, making them available for other organisms. Without fungi, ecosystems would be overwhelmed by dead organic matter, and essential nutrients would not be continuously replenished.

Describe the structure of a fungus, including description of the cells that make up the hyphae.

The body of a fungus is built from hyphae, which are long chains of cells surrounded by a chitin cell wall. Many hyphae are separated by cross-walls with pores, allowing ribosomes, mitochondria, and nuclei to flow freely between cells. In some fungi, there are no cross-walls at all, leaving a continuous mass of cytoplasm with many nuclei.

How are mushrooms formed on a mycelium?

Mushrooms begin as small buds on the underground mycelium. When conditions are favourable (such as after rain), rapid water absorption increases internal pressure, pushing the developing mushroom upward until it emerges above ground.

What is the function or purpose of a mushroom structure on a fungus?

Mushrooms are reproductive structures. They produce spores at the tips of specialized hyphae, which are then released into the air for dispersal, allowing the fungus to spread to new environments.

Fungi grow at a very high rate (quickly). Explain this.

Because hyphae extend only at their tips and do not thicken, fungi can rapidly spread through a food source. This allows them to efficiently colonize new territory and maximize nutrient absorption.

How does a mycelium show the relationship between structure and function?

The structure of a mycelium—made of countless fine, branching hyphae—gives it an enormous surface area. This maximizes its function of secreting enzymes and absorbing nutrients. In other words, its design (thin, widespread filaments) directly supports its feeding strategy.

How are mycorrhiza and plant roots connected? This is a symbiotic relationship, what advantages do the mycorrhiza and plant get from the relationship?

• In mycorrhizae, fungal hyphae either penetrate or surround plant root cells.

  • Benefit to the plant: The fungus absorbs phosphorus and minerals from the soil and makes them available to the plant.

  • Benefit to the fungus: The plant provides sugars made during photosynthesis, which nourish the fungus.

• This mutualism has been crucial for plant survival and success on land, as it greatly improves nutrient acquisition.

Reproduction is done through the release of spores. How are spores dispersed and what causes their germination?

• Fungal spores are typically haploid and are produced in very large numbers. They are lightweight and easily dispersed by wind, water, or sometimes animals.

• Germination occurs when a spore lands in a moist environment with available nutrients. Under these favourable conditions, the spore undergoes mitosis and grows into a new haploid mycelium.

Describe in detail the life cycle of a fungus including haploid, diploid, and heterokaryotic stages, mitosis and meiosis, and sexual and asexual reproduction.

• Haploid stage: Most of a fungus’s life cycle is spent as haploid mycelia, which grow and reproduce asexually by mitosis, forming spores directly.

• Sexual reproduction:

  1. Plasmogamy – Cytoplasms of two different mating-type hyphae fuse, but nuclei remain separate.

  2. Heterokaryotic stage – Cells contain two or more distinct haploid nuclei. This stage can last hours to centuries.

  3. Karyogamy – Fusion of the parental nuclei occurs, creating a diploid zygote.

  4. Meiosis – The diploid phase is short-lived. Meiosis restores the haploid state, producing haploid spores.

• Asexual reproduction: Haploid mycelia produce spores through mitosis without undergoing plasmogamy, karyogamy, or meiosis. This allows fungi to reproduce rapidly and colonize new habitats.

• Key point: Fungal reproduction alternates between sexual and asexual cycles, with haploid and heterokaryotic stages dominating, while the diploid stage is brief.

List characteristics of molds.

• Rapidly growing fungi.

• Reproduce asexually by producing spores, often at the tips of specialized hyphae.

• Commonly appear as fuzzy carpets on organic matter such as bread, fruit, or damp surfaces.

• Most molds are classified as imperfect fungi, since only their asexual reproduction is known.

List characteristics of yeasts.

• Single-celled fungi rather than filamentous.

• Reproduce asexually, usually by budding (a small cell pinches off from the parent).

• Found in moist or liquid habitats, including plant sap, animal tissues, and sugary environments.

• Some yeasts (like Saccharomyces cerevisiae) are important in bread, beer, and wine production, while others can be pathogens.

What percentage of the hypothesized fungi have been described?

Fewer than 10% of fungal species have been described. About 100,000 species are currently known, but metagenomic studies suggest that total fungal diversity is likely in the millions.