Plants

Eukaryotes: All land plants are eukaryotic organisms.
Photoautotrophs: Most land plants synthesize their own food via photosynthesis.
Multicellular: All plants are multicellular organisms.
Cell Walls: Plant cells possess rigid cell walls made of cellulose.
Sessile: Plants do not move; they are stationary organisms.
Life Cycle: All plants have an alternation of generations:
- Alternates between a haploid gametophyte stage (n) and a diploid sporophyte stage (2n).
Embryo Development: In land plants, the embryo develops within the gametophyte tissue.

Zygote: Formed by fertilization of gametes (n).
Sporophyte (2n): The diploid phase that develops from the zygote.
Gametes (n): Haploid reproductive cells produced by meiotic division in the sporophyte.
Meiosis: Process in sporophyte to produce haploid spores (n), which grow into gametophytes.

Root and Shoot Adaptations: Roots and shoot systems evolved for nutrient uptake and structural support.
Dominance of Diploid Phase: In the life cycle of plants, the diploid sporophyte became the dominant phase.
Separate Male and Female Gametophytes: Evolution of some vascular plants led to distinct male and female structures.

Contains approximately 300,000 living species across 10 phyla.
Adaptations:
- Avoidance of desiccation.
- Improved physical support.
- Efficient nutrient uptake mechanisms.
- Ability to reproduce sexually without reliance on water.
Shared Traits with Green Algae:
- Cellulose cell walls, storage of photosynthetic starch, and presence of chlorophylls a and b.
- Algal ancestors probably transitioned to land around 450 million years ago.

Cuticle: A waxy layer on leaf surfaces to reduce water loss.
Stomata: Pores in the epidermis for gas exchange, allowing regulation of water loss.

Evolution from haploid to diploid dominance observable through various plant groups:
- Sequence: Green algae -> Bryophytes (e.g., liverworts, hornworts, mosses) -> Vascular plants (e.g., lycophytes, ferns, gymnosperms, angiosperms).

Types: Liverworts, hornworts, and mosses, which lack vascular tissue.
Characteristics:
- Poikilohydric: Limited control over water content.
- Typically small and thrive in wet environments but can also inhabit dry areas.

Mature Sporophyte: Functions in reproduction, topped by sporangia that release spores (formed by meiosis).
- Zygote Development: Remains in the archegonium while developing into a mature sporophyte.
- Gametophyte Formation: The spore germinates to form a protonema, leading to the development of gametophytes with antheridia (male) and archegonia (female).
- Fertilization: Flagellated sperm swims to the egg in a moist environment for fertilization.

Characteristics: Flourished in moist habitats; include ferns and lycophytes, which have specialized vascular tissues.
Heterospory: Some seedless vascular plants can produce two types of spores (male and female).

Gymnosperms:
- Characteristics: Seed-producing plants that do not enclose their seeds.
- Reproductive Adaptations: Non-motile sperm, with pollination occurring via wind.
- Types: Includes coniferophyta (conifers), cycadophyta (cycads), ginkgophyta (Ginkgo biloba), and gnetophyta (gnetophytes).
Angiosperms:
- Characteristics: Flowering plants with enclosed seeds.
- Distinct Features: Include carpels that protect ovules, major groups being monocots and eudicots, have co-evolved with pollinators.

Efficient Transport Systems: Enhanced vascular tissue for improved water and nutrient movement.
Double Fertilization: Resulting in the formation of both an embryo and a triploid endosperm (nutrient tissue for the growing embryo).
Protection of Ovules: The ovary develops into fruit, providing protection and facilitating seed dispersal.

Flowering plants have evolved features that attract specific animal pollinators, improving fertilization success.