Difficulty: Introductory to Intermediate | Prerequisites: Domains of Life, Cell Types and Protists notes.
This set of notes covers cell division (mitosis and meiosis), the characteristics and reproduction of fungi, plant evolution and adaptations, and the reproductive strategies of seed plants. If you have not reviewed prokaryotic vs eukaryotic cell structure, start there.
Cells divide by mitosis (for growth and repair, producing identical copies) or meiosis (for sexual reproduction, producing genetically varied gametes with half the chromosomes). Fungi are heterotrophic decomposers with chitin cell walls that reproduce via spores. Plants evolved from green algae, developed vascular tissue and seeds to colonise land, and alternate between haploid and diploid generations.
DNA (deoxyribonucleic acid)
The molecule that carries an organism's genetic instructions, organised into chromosomes.
Chromosome
A structure of tightly coiled DNA and associated proteins that contains many genes. Think of it as one volume in the full instruction manual for building and running an organism.
Gene
A segment of DNA that encodes a functional product (usually a protein). In simple terms, a gene is one specific instruction within a chromosome.
Diploid (2n)
A cell containing two complete sets of chromosomes, one from each parent. Most body (somatic) cells in mammals are diploid.
Haploid (n)
A cell containing one set of chromosomes. Gametes (sperm and egg cells) are haploid.
Mitosis
Cell division that produces two genetically identical diploid daughter cells. Essential for growth, repair, and asexual reproduction.
Meiosis
Cell division that reduces chromosome number by half, producing four genetically unique haploid gametes. Critical for sexual reproduction and genetic variation.
Chitin
A tough polysaccharide that forms the cell walls of fungi (and the exoskeletons of arthropods). Think of it as the fungal equivalent of cellulose in plants.
Zygomycota
A phylum of fungi that reproduce sexually via zygosporangia and asexually via sporangia. Bread mould (Rhizopus) is a common example.
Ascomycota
The "sac fungi," which produce sexual spores (ascospores) inside sac-like structures called asci, and asexual spores (conidia) from conidiophores.
Basidiomycota
The "club fungi," which produce sexual spores (basidiospores) on club-shaped structures called basidia. Mushrooms are the familiar example.
Mycorrhizae
Mutualistic associations between fungi and plant roots in which the fungus helps the plant absorb water and minerals in exchange for sugars.
Cellulose
A structural polysaccharide that forms plant cell walls, providing rigidity and support.
Alternation of generations
A life cycle in which a multicellular haploid stage (gametophyte) alternates with a multicellular diploid stage (sporophyte). Characteristic of all land plants.
Vascular tissue
Specialised transport tissue in plants: xylem carries water and minerals upward; phloem distributes sugars throughout the plant.
Gymnosperm
A seed plant that produces naked seeds (not enclosed in a fruit). Conifers are the most familiar group. Often wind-pollinated.
Angiosperm
A flowering plant that produces seeds enclosed within a fruit. The most diverse group of land plants, using flowers for pollination and fruits for seed dispersal.
Sepal, petal, stamen, carpel
The four main flower structures. Sepals protect the bud, petals attract pollinators, stamens produce pollen (male), and carpels contain ovules (female).
DNA is organised into chromosomes, each carrying many genes
Diploid cells (2n) have two chromosome sets (e.g. human body cells: 46 chromosomes)
Haploid cells (n) have one set (e.g. human gametes: 23 chromosomes)
Mitosis produces two identical diploid daughter cells
Purpose: growth, tissue repair, asexual reproduction
Meiosis produces four genetically unique haploid cells
Purpose: producing gametes for sexual reproduction
Introduces genetic variation through crossing over and independent assortment
Eukaryotic, mostly multicellular, heterotrophic (absorb nutrients externally)
Cell walls made of chitin
Reproduce both sexually and asexually via spores
Major phyla and their reproductive structures:
Zygomycota – zygosporangia (sexual), sporangia (asexual)
Ascomycota – asci with ascospores (sexual), conidiophores with conidia (asexual)
Basidiomycota – basidia with basidiospores (sexual)
Most fungi spend the majority of their life cycle as haploid organisms; sexual reproduction is often triggered by environmental stress
Ecological roles: decomposition (recycling nutrients), mutualistic relationships (mycorrhizae with plant roots), and production of economically important products (penicillin, bread, beer)
Plants are eukaryotic, multicellular photoautotrophs with cellulose cell walls
Evolved from green algae, adapting to life on land
All land plants exhibit alternation of generations: a haploid gametophyte generation alternates with a diploid sporophyte generation
Key evolutionary adaptations for land:
Vascular tissue (xylem and phloem) for long-distance transport of water and nutrients
Roots and stems for support and nutrient uptake
Seeds for dispersal and dormancy
Non-vascular plants (e.g. mosses) lack vascular tissue, remain small, and require moist environments
Seedless vascular plants (e.g. ferns, horsetails) have vascular tissue but reproduce via spores rather than seeds
Seed plants have a dominant sporophyte generation; the seed protects and nourishes the developing embryo
Gymnosperms produce naked seeds (not enclosed in fruit), are often wind-pollinated, and include conifers, cycads, and ginkgoes
Angiosperms (flowering plants) are the most diverse plant group
Flowers contain sepals, petals, stamens (male), and carpels (female)
Fruits enclose and protect seeds, aiding dispersal
Dispersal mechanisms: wind, water, animals (insects, birds, mammals)
The evolution from spore-based to seed-based reproduction was a major adaptation, allowing plants to colonise drier habitats
Students frequently confuse mitosis and meiosis. Mitosis produces two identical diploid cells; meiosis produces four unique haploid cells. They serve different purposes.
Fungi are not plants. They lack chlorophyll, do not photosynthesise, and have chitin (not cellulose) in their cell walls. They are heterotrophs.
"Alternation of generations" does not mean a plant switches between sexual and asexual reproduction. It means the organism alternates between a multicellular haploid form (gametophyte) and a multicellular diploid form (sporophyte).
Students sometimes assume all seed plants have flowers. Gymnosperms produce seeds but have no flowers or fruits; only angiosperms are flowering plants.
⚠️ Be able to compare mitosis and meiosis side by side: number of divisions, number of daughter cells, ploidy of products, and biological purpose.
⚠️ Know the distinguishing features of the three major fungal phyla (Zygomycota, Ascomycota, Basidiomycota) and their reproductive structures.
⚠️ Understand the progression from non-vascular plants to seedless vascular plants to seed plants, and which adaptations arose at each stage.
⚠️ Be able to label the four parts of a flower (sepal, petal, stamen, carpel) and state the function of each.
⚠️ Know what mycorrhizae are and why they matter ecologically.
True or False: Mitosis produces four haploid daughter cells. Answer: False. That describes meiosis. Mitosis produces two diploid daughter cells.
Fill in the blank: Fungal cell walls are made of ______, whereas plant cell walls are made of ______. Answer: chitin; cellulose.
True or False: Gymnosperms produce seeds enclosed in fruits. Answer: False. Gymnosperm seeds are naked (not enclosed in fruit). Seeds enclosed in fruits are an angiosperm trait.
Fill in the blank: In alternation of generations, the haploid stage is called the ______ and the diploid stage is called the ______. Answer: gametophyte; sporophyte.
True or False: Ferns are seed plants. Answer: False. Ferns are seedless vascular plants that reproduce via spores.
Q: Compare and contrast mitosis and meiosis in terms of the number of daughter cells, ploidy, and biological function.
A: Mitosis produces two genetically identical diploid (2n) daughter cells and serves growth and repair. Meiosis involves two rounds of division, producing four genetically unique haploid (n) cells (gametes) for sexual reproduction. Meiosis introduces genetic variation through crossing over and independent assortment; mitosis does not.
Q: How do fungi obtain their nutrition, and why are they classified separately from plants?
A: Fungi are heterotrophs that obtain nutrients by secreting digestive enzymes onto their food source and absorbing the broken-down molecules. They lack chlorophyll and cannot photosynthesise. Their cell walls contain chitin rather than cellulose. These differences place them in their own kingdom, separate from plants.
Q: Describe the key evolutionary adaptations that allowed plants to move from water to land.
A: Major adaptations include vascular tissue (xylem and phloem) for transporting water and nutrients over long distances, roots and stems for structural support and nutrient uptake, a waxy cuticle to prevent water loss, stomata for gas exchange, and seeds (in later lineages) for reproduction in dry environments without dependence on water for fertilisation.
Q: What is the difference between a gymnosperm and an angiosperm? Give one example of each.
A: Gymnosperms produce naked seeds not enclosed in a fruit (e.g. pine trees). Angiosperms are flowering plants that enclose their seeds within fruits (e.g. apple trees). Angiosperms use flowers to attract pollinators and fruits to aid in seed dispersal.
Genetics and cell division link back to evolution: meiosis generates the genetic variation that natural selection acts on. Fungi connect to ecology through decomposition and mycorrhizal relationships with plants. Plant evolution and seed strategies reappear when studying animal diversity, because many animals co-evolved with angiosperms as pollinators or seed dispersers.
DNA, chromosome, gene, diploid, haploid, mitosis, meiosis, cell division, gamete, crossing over, fungi, chitin, Zygomycota, Ascomycota, Basidiomycota, mycorrhizae, spore, decomposer, cellulose, alternation of generations, gametophyte, sporophyte, vascular tissue, xylem, phloem, non-vascular plant, moss, fern, seedless vascular plant, gymnosperm, angiosperm, flower, sepal, petal, stamen, carpel, pollination, seed dispersal, BIO 101