BIOL 1010 | Chapter 17

define charophytes

Green algae closely related to plants. They are photosynthetic eukaryotes, often multicellular, and share structural and genetic similarities with land plants. Modern charophytes like Chara and Coleochaete resemble the algal ancestors of land plants, which lived in shallow waters subject to occasional drying.

define stomata

Tiny adjustable pores found on the surface of leaves and stems. They regulate gas exchange by allowing CO₂ in for photosynthesis and O₂ out, while also helping to control water loss by closing when conditions are dry.

define apical meristems

Growth-producing regions at the tips of roots and shoots. These regions contain actively dividing cells that allow plants to elongate, branch, and maximize exposure to resources both underground (water, minerals) and aboveground (light, CO₂).

define vascular tissue

A network of specialized cells forming tubes that transport water, minerals, and sugars throughout the plant. It connects subterranean roots with aerial shoots and leaves.

define xylem

The vascular tissue made up of dead, lignin-reinforced cells that form microscopic pipes. Its function is to transport water and dissolved minerals from the roots upward through the plant body.

define phloem

The vascular tissue made up of living cells. Its function is to distribute sugars (products of photosynthesis) from leaves to roots and other parts of the plant.

define lignin

A strong chemical compound embedded in plant cell walls. It reinforces and strengthens xylem cells, providing rigidity and structural support that allows vascular plants to grow tall

define gametangia

Multicellular structures in which gametes (eggs and sperm) are produced and protected by a layer of sterile cells. Eggs remain within the female gametangium, while sperm must reach them, usually through water.

define pollen grains

Structures in seed plants containing sperm-producing cells. Unlike swimming sperm of mosses/ferns, pollen can be transported by wind or animals, removing the need for water in fertilization.

define zygote

The diploid cell formed after fertilization, when a sperm cell unites with an egg cell. In plants, the zygote develops into an embryo while still attached to, and nourished by, the parent.

define embryophytes

Another term for land plants. The name refers to their defining trait: having multicellular, dependent embryos that are retained and nourished by the parent plant.

define haploid

one set of chromosomes; gametes (eggs and sperm) are haploid.

define diploid

two sets of chromosomes; zygotes and sporophytes are diploid.

define sporangia

Protective structures in the diploid (sporophyte) stage where meiosis occurs to produce haploid spores.

define spore

A single haploid cell capable of developing into a multicellular organism without fertilization. Spores are protected by tough walls and serve in reproduction and dispersal (especially in mosses and ferns).

define seeds

Structures containing a plant embryo, a food supply, and a protective coat. Seeds are more complex than spores and provide enhanced protection, nourishment, and dispersal ability.

define seedless plants

Plants that reproduce and disperse by spores rather than seeds (e.g., mosses and ferns).

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.

define bryophytes

Informal group of seedless, nonvascular plants (mosses, liverworts, hornworts) that lack lignified tissues, true roots, and leaves but have apical meristems and dependent embryos.

define nonvascular plants

Plants that lack vascular tissue (xylem and phloem) and lignin, which limits their size; includes bryophytes.

define vascular plant

Plants with lignified vascular tissues (xylem and phloem), enabling structural support, tall growth, and efficient transport of water and nutrients.

define lycophytes

A clade of seedless vascular plants, including club mosses; among the earliest vascular plants.

define monilophytes

A clade of seedless vascular plants, including ferns and their relatives; most diverse in the tropics.

define seed

A plant embryo packaged with a food supply and protective covering, allowing survival and dispersal in terrestrial habitats.

define pollen

Structures containing sperm-producing cells that can travel long distances by wind or animals, eliminating the need for water in fertilization.

define gymnosperms

Early seed plants whose “naked” seeds are not enclosed in protective chambers; include conifers, cycads, ginkgo, and Ephedra.

define conifer

The largest clade of gymnosperms, consisting of cone-bearing trees like pine, spruce, and fir.

define angiosperms

Flowering plants that produce seeds enclosed within protective chambers (fruits); the most diverse plant group.

define flowers

Complex reproductive structures of angiosperms that produce gametes and seeds within protective chambers.

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).