Bryophytes

• 290,000+ known species of land plants: mosses, ferns, gymnosperms, flowering plants

Evolution of Land Plants

• Timeline
  • 1.2 bya — thin coating of cyanobacteria and protists, likely close to water
  • 500 mya — small plants, fungi, and animals on land
  • 470 mya — numerous fungal spore fossils
    • sporopollenin
  • 385 mya — taller plants (lignin)
• Plantae clade/supergroup, Viridiplantae, Streptophyta
  • Land plants: Embryophytes
  • Exclusive of charophytes
• Proteins that synthesize cellulose are arranged in a rosette, with sub-units derived from inside the cell center vs. linear proteins
• Chara — stonewort (calcium carbonate)
• Coleochaete — sporopollenin
• Land plants have various opportunities and challenges
  • More sunlight, more CO2 available
  • Nutrients no longer bathe plants (mycorrhizae), issues competing for sunlight
  • All plants adapt to dry land via
    • Alteration of Generations lifecycle
      • Oogamous
      • vs. charophytes
      • spores are protected against dessication and can opt to grow into gametophyte
    • Multicellular sporangia that produce “Walled spores”
      • Division/differentiation for walls
      • Sporopollenin: Spores and pollen greens, tough and resistant, hard to digest
    • Multicellular gametangia in most plant phyla
      • Multiple cells protecting the egg and sperm being made
      • Consistent structure
      • Egg producing gametangium is the archegonium
        • Flask/pear shaped
        • Has a larger venter (egg) and a neck that sperm swims through
      • Sperm producing gametangium is the antheridium
        • Oval/spherical
      • Surrounded by a layer: sterile jacket; both outside on the gametangiumm and on each individual
    • Multicellular young sporophyte is retained and nourished by the parent: embryo
      • Advancement over single zygotes not protected/nourished
    • 3-dimensional apical meristems
      • three-dimensional grrowth vs. intertwined filaments (parenchymatous) growth

Bryophytes

• Non-vascular plants; no vascular tissue
• Paraphyletic group/Grade of evolution
• No lignin for conducting cells of xylem → no true vascular tissue
• May have rhizoids: unicellular or filamentous structures that anchor the plant in place; no need for absorptive structure, can dessicate
• No true leaves; no veins/vascular tissue (no roots, stems)
• Gametophyte is the dominant generation
  • Bisexual or Unisexual
  • Male gametophyte is a antheridium sperm, female is an archegonium sperm
  • Releases and swims through a film of water; fertilizes egg and forms a diploid zygote
  • Zygote divides through mitosis to form embryo, then sporophyte
  • One spore producing structure: sporangium
  • Meiosis of diploid cells: sporocytes
• Swimming sperm
• Dominant gametophyte, reduced and dependent sporophyte

Bryophyta

• Mosses phylum
• Leafy area at bottom is dominant gametophyte
• Stalk is the sporophyte; non-dominant, ephemeral
• Three classes of mosses
• Wet/moist areas, cold, volcanic area
• Spiral arrangement of “leaves” around the central axis
• Upright growth supported by thicker cell walls, not lignin
• Can completely dry out and rehydrate; poikilohydry
• Mostly haploid; two part haploid stage
  • Haploid spores germinate and form filamentous green mass: protonema(ta)
  • Bulbles/buds: main part of gametophyte developing
  • Gives rise to leafy gametophyte
    • Many are bisexual, but have different stems that are unisexual
    • Some are single-sex
    • Sexual structures are on top of gametophyte, on top of stem: antheridial/archegonial head
      • Sterile hairs
      • Archegonial head has longer, stalked structures beneath venter
      • Venter is torn in two, then carried upwards and enlarges: calyptra
      • Venter falling off allows spore dispersal; leaves cap of sporangium (operculum) and peristome teeth that disperse spores
    • Three parts of gametophyte
      • Capsule: Sporangium
      • Seta: Stalk
      • Foot: Anchors to gametophyte
    • Characteristics of sporophyte
      • Dependent on gametophyte for nutrition; turns brown quickly aand no longer photosynthetic
      • True stomata with one cell vs. guard cells; some contrrol over dessication
      • Larger sporophytes have specialized cells for water and transport; water hydroids and leptoids

True mosses

• Polytrichum (hair/cat moss)

Peat mosses

• Sphagnum spp.
• Wetlands
• Marginally different gametophyte: “stemmed”/branched/tufted gametophytes
• Leaf layer has two types of cells
  • Living cells: green, narrow, networked
  • Dead cells: large cells with ridges of thick cell wall and pores
    • Holds a lot of water
    • Soil mixtures, soil bags
• Contains decay-resistant phenolics
  • Antiseptic and anti-microbial properties
  • Wound dressings in WW2 (pus, growth of bacteria), Native diapers, soils
• Acidifies habitat
  • Prevents decomposition
  • Secretes acids, protons
  • Layers build up and don’t decompose: carbon remnants; source of fuel
  • Floating mat bogs: layer of moss accumulates soil, allowing vegetation floating on open water
  • Bogmen left behind, preserved with hair and skin; “Tollund Man”
  • Ecological importance: 3% of land mass and accumulate 30% of soil carbon
    • vs. dessication via climate change; increased rates of decomposition and carbon release
• Peat: compressed, partially decomposed plant matter
  • Peat can buildup in waterlogged soils without moss; more with peat moss

Liverworts

• Hepatophyta spp. — Liver phylum
• Lobed
• “Doctrine of signatures”
• Leafy liverworts and thallose liverworts
  • Tropical leafy liverworts: leaflike structures that are tiny; more common
  • Thallose liverworts have a thallus instead of large differentiation
• Thallose branches dichotomously/diverges
  • Flat on the ground
  • ~2cm wide
  • Thallus serves as the dominant gametophyte
  • Non-green cells on bottom hold water; green cells on top
  • No true stomata; only open pores that close when the plant dessicates
• Thallose liverworts have asexual and sexual reproduction
  • Gemmae cups/splash cups produced by mitosis: multicellular packets
    • Splash cups; grow into new gametophyte thallus
  • Reproductive structures are unisexual; can only be discerned after “fruiting”
    • Long stalks; antheridial heads/antheridial fours, archegonia heads/fours
      • Flat antheridial heads, leafy archegonia heads
      • Archegonia heads have hanging archegonia; sperm must be splashed or swum up to fertilize egg
        • Generates microscopic sporophyte with a foot, short seta, and large sporangium capsule
        • Dispersed spores from top when dry
• Marchantia

Hornworts

• Anthocerophyta spp.
• The horn is the sporophyte; sporophyte is the sporangium
• Short stalk and a short foot
• Sporangium continuously grows, and splits topdown as spores release
• Tetrad: four spores
• True stomata

Seedless vascular plants

• Grade of evolution
  • Ancestral vascular tissue; no extant seeds
• Divided into Lycophytes (club mosses, spike mosses, quillworts) and monilophytes (ferns, horsetails, whisk ferns)
• Has lignin in the tracheids and vessel elements in the xylem
• Reconstructed ancestor may not have had vascular tissue (Aglaophyton) but had branched sporophyte stems that could produce multiple sporangia
• Sporophyte is the dominant generation
• Spores aid in dry adaptations: protects pollen
• Various characteristics
  • True vascular tissue and lignin in the xylem conducting elements
  • Cuticles and true stomata protect water loss and gas exchange
  • Sporophyte is the dominant generation and is longer lasting or larger
  • Both generations are nutritionally and physically independent
    • Gametophytes can be either underground and dependent upon mycorrhizae or aboveground and green
  • Sperm are flagellated and need free water for fertilization
  • Most plants have roots; some do not
  • True stems with vascular tissue (stele)
  • True leaves
  • Plants have spores and sporangia
• Stems have developing stele: vascular tissue present in the stem or root
  • Early development: protostele
    • Irregular development
    • Solid core of central vascular tissue
  • Siphonostele
    • A pith with a ring of vascular tissue
    • Siphon-like
    • May have leaf gaps or no leaf gaps
  • Eustele/True stele
    • Vascular bundles
    • Bundles are able to merge and come apart
  • Eustele and siphonostele evolved independent of one another
• Most groups have true leaves with vascular tissue and veins; two types
  • Microphyll
    • Monovein leaves
    • Particular evolutionary line: the enation theory
      • a protostele stem without leaves developed flaps of green photosynthetic tissue
      • enations: flaps of green photosynthetic tissue that increased surface area for photosynthesis but were not venated
      • vascular supply was redirected to enation, developing a vein and a microphyll
    • Selaginella kraussiana
  • Megaphyll
    • Polyvein leaves
    • Hymenophyllum tunbridgense
    • Telome theory
      • Telome: end branches of the megaphyll
      • A green stem that dichotomously branched in three-dimensions (bushy) developed equal dichotomous branches
      • Overtopping: a main stem developed, with one branch becoming unequally larger while the side branch remaining continued to branch
      • Planation: the side branch flattened onto a plane, forming the basis for the veins of the megaphyll leaf
      • Webbing: green tissue that was not venated branches out, forming the megaphyll
• Two types of spores/sporangia: homosporous and heterosporous
  • Homosporous
    • Monodic spore that grows into a bisexual gametophyte
    • Gametophyte contains both sexes of gametangia
  • Heterosporous
    • Two types of spores
    • Spores develop into unisexual gametophytes
• Reduced and independent gametophyte, dominant sporophyte

Lycophyta

• Monophyletic phyla
• Lycophytes
• Three extant families
  • Phylum was prevalent in Carboniferous era in swamps
    • carbon today comes from living plants
    • tree-sized lycophytes in swamps and free standing water; present species are very small
  • Protosteles and microphylls
    • Regardless of actual size of microphylls
  • Bean-shaped sporangia

Spike Mosses

• Selaginella moellendorffii; only Selaginella genus
• Selaginellaceae
• Underground rhizomes with true roots
• Aboveground aerial stems with spiral microphylls
• Heterosporous with reduced gametophyte size
• Some spike mosses are tender and flattened (ironlike/planated); some are spiked
• Resurrection plant: xerophytic, can dry completely and rehydrate
• Megasporangium are on megasporophyll and develop megaspores
  • Megaspore develop into female gametophytes (megagametophyte) that develop eggs
• Microsporangium are on microsporophyll and develop microspores
  • Microspore develop into male gametophytes (microgametophyte) that develop sperm
• Particular lifecycle
  • Megaspore develops a sporophyte
  • Sporophyte matures devloping roots and strobili
  • Strobili contain
    • one megasporangium that contains one diploid megasporocyte
      • Megasporocyte goes through meiosis and develops four megaspores
    • many microsporangium
      • many microsporocytes developing four microspores in meiosis
    • No particular arrangement off megasporangium and microsporangium
  • Free-sporing release
    • Microspore dividees by mitosis and eventually develops motile sperm
    • Megaspore wall develops a protruding megagametophyte wwith archegonia to fertilize

Club Mosses

• Diphasiastrum tristachyum, Lycopodium spp., Huperzia
• Lycopodiaceae family
• Underground rhizomes with true roots branching
• Aboveground aerial stems with spiral microphylls
• Homosporous and potentially bisexual
• Commonly identified by “clubs”: strobili clusters of sporophylls
• Sporophyte contains particular protostele regardless of sample
  • Solid mass of vascular tissue
  • Interconnected plates of xylem with phloem borders
• Lateral bean-shaped sporangia
• Sporophylls: leaves that also hold sporangia
• Strobilus: compact arrangement of sporophylls and sporangia
• Sporocytes
• Free-sporing lifecycle: spores are released before gametophytes are generated

Quillworts

• Isoetes gunnii; Isoetes genus, Isoetaceae family
• Wetlands
• Contractile roots that anchor into drying mud
• CAM photosynthesis

Monilophyta

• Monilophytes
• Three subphyla/families

Ferns

• Largest family; ~11,000
• Athyrium filix-femina
• Many species are tropical
  • Many species are epiphytic; lives on other plants
    • Some epiphytic species are not tropical
    • Commensalist
• Siphonosteles: Cylindrical piths that may have leaf gaps
• “Leaves” are fronds; fronds are megaphylls
  • Polyvenation
  • Fronds are divided into leaflets (pinnae) and can have secondary subdivision; high division
  • Fronds are typically the only part above ground; rhizome is belowground and roots branch from rhizomes
• Ferns make “fiddleheads” when young leaves are growing
  • Tight scroll of leaf cells
  • Differential cell enlargement
  • Uncurling and straightening leaves flatten out into mature leaves
  • Protects young tissue
  • May store toxins
• Numerous “typical” ferns

Filicales

• Majority of ferns in this order
• Leptosporangium unique to Filicales
  • Annulus specialization: a row of cells specialized to open up sporangia and catapult spores out
• Homosporous
• Group of sporangia: sorus (sori)
  • May be protected by a flap of tissue: indusium
    • “Upside-down umbrella” shape
    • Indusium shrivels and allows spores to free
    • Variety of indusia shapes: bean-shape etc.
• Mature gametophyte is small, heart-shaped
  • Base of sporophyte; anchored by rhizoids
  • Non-dominant generation
  • Fully absorptive tissue
  • Notch and tip at center with an archegonia close to the notch and antheridia close to the tip
  • Typically bisexual
  • Flimsy green one-layer cells
• Sporophyte has notable vascular tissue

Eusporangiate

• Has a eusporangium
  • Thick sporangia with no annulus
• Botrychium, Ophioglossum
• large sporangia
• Many tree ferns are eusoporangiate

Water Ferns

• Aquatic
• Heterosporous
• Marsilea, Azolla

Horsetails

• Equisetum telmateia
• “Scouring rushes”
• Equisetum genus
• Some are branched; horse-tail appearance (branches, not leaves)
• Some do not have branches; different stems
  • Diverse vegetative and fertile stems
  • Fertile stems have strobili
• Large airspaces
  • Carinal canals
  • Wet areas that require oxygen exchange and water transport between roots and shoots
• Tree-sized horsetails in carboniferous era (360mya)
• Microphylls reduced from megaphylls; different origin of microphylls
• Hollow stems with carinal canals
• Large amounts of silica in epidermis; rough ridges
  • Scouring rushes
• Solid jointed nodes; jointed stems that are photosynthetic
• Sporangia are arranged in umbrella-shaped strobili with sporangiophores
  • Modified stems: sporangiophores
  • Multiple sporangia hang from end of sporangiophores
• Special spore dispersal using elaters
  • Spores have ribbonlike parts in spore wall that detach: elaters
  • Opens and wing like when dry; wraps around spore when moist

Whiskferns

• Psilotum nudum
• Only Psilotum and Tmesipteris genera
• Formerly “primitive”; enations are hypothesized reduced from true leaves
• Tropical

Seed Plants

• Gymnosperms and angiosperms
• Reduced and dependent gametophyte, dominant sporophyte
• Heterosporous
• No free-sporing behavior before gametophyte development; release after gametophyte development
• Reduction and loss of structures
• Pollen grains and ovules
  • Pollen grains transfer in pollination and fertilize; sperm do not have to swim
    • Pollination: transfer of pollen from pollen grain to ovary
    • Fertilization: sperm fuses with egg
  • Ovules become seeds after fertilization; better dispersal units to spores
• Present in Carboniferous era, but greatly diversified during Permian period duee to changes in climate
  • Warm/wet to dry/cold change
  • Colder, drier, seeds and pollen grains were advantageous
• True secondary growth
  • Increased competition for sunlight

Pollen Grains

• Male gametophytes with coating material
• Do not require water for fertilization
• Not free-sporing
  • Microspores divide by mitosis to make pollen grains, then release from microsporangia
• Sporopollenin wall; prevents dessication
• Four cells in cone; tetradic
• Transferred by air pollination
• Creates two sperm and a pollen tube

Ovules/Seeds

• Immature seeds are ovules
  • Protective layer of cells: integument
    • May be multiple
    • Diploid sporophyte tissue
    • New structure
  • Integument houses megasporangium
    • “Nucellus”; fleshier than previous megasporangium
      • Nucellus dooes not proliferate; most space after fertilization is the megagametophyte
    • One megaspore develops; four developed, but three break down
  • Hole in integument: micropyle
    • Fertilization/pollen tubes
• After fertilization, it is called a seed
  • Zygote develops into embryo; mitosis
  • Has a food supply
    • Food supply is the megagametophyte
  • Integument becomes seed coat
  • Micropyle seals off
• Seeds are dormant until good for growth

Gymnnosperms

• Naked seed plants
  • Seeds are exposed to air; no fruiting
• Multiple phyla
  • Coniferophyta
    • Conifers
    • Cone-bearing trees
    • Representative

Coniferophyta

Reproduction

• Male cones: Strobili
  • Relatively small, soft, non-woody
  • Only used to make pollen grains
  • Leaves (microsporophylls) arrange around a central axis
    • Each microsporophyll bears 2 pollen sacs or microsporangia
• Microsporocytes develop via meiosis to make microspores, microspores develop via mitosis to make pollen grains
• Pollen grains are released from cones
  • Two prothallial cells: part of the body of the male gametophyte
  • Generative cell: Large central cell that develops the two sperm
  • Tube cell: develops the pollen tube
  • Large air sacs on sides that allow for air dispersal
• Tube cell directs fertilization of pollen tube
  • Non-fertilizing sperm breaks down
• Female cones (ovulate cones)
  • Central axis is surrounded by cone scales
    • Cone scales; bracts
    • Bracts are modified leaves
    • Cone scales are more than leaves; encompasses the bract and the bud/stem; not a megasporophyll
      • Cone scales are under the ovule
  • Space between scales allows pollen grain to enter
  • Between spore release, scales are shut
• Megasporocyte divides by meiosis to make four megaspores, megaspore divides by mitosis to make a large megagametophyte (thousands of cells)
• Pines have large genomes used in studying
• Winged seeds; wind dispersal
• Also bird or animal dispersal
  • Insect pollination

Diversity

• Pines (Pinus), firs, Douglas-firs, Sequoia, European larch, juniper, cypress, yew
• Mostly isogamous monoecious
• Secondary growth
• Needle-like leaves
  • Reduced surface area
  • Less vaporization and evaporation
  • Pinus bundles
• Tracheids; true vascular tissue
  • No vessels
• High importance: Large swaths in northern coniferous forests (Taigas)
  • Norway
  • Fewer species, but cover large areas of land

Cycadophyta

• Cycads, Sago palms
• Dioecious
  • Haustorial pollen tube
  • Feeding tube that ruptures open to release sperm in ovule

Ginkgophyta

• Gingko biloba — Maidenhair tree
• Deciduous
• Not evergreen
• Dioecious
• Fleshy, rancid seed coasts with tasty kernals
• Lobed leaves

Gnetophyta

• Welwitschia, Ephedra, Gnetum
• Some have vessels and some lack archegonia
• Not ancestors to angiosperms; convergent evolution
• Dioecious

Angiosperms

• Highly successful
  • All have vessels in xylem
  • Direct pollination with animals; less waste
    • Co-evolution with insect pollinators
  • Fruits and their help with seed dispersal

Evolution

• Around for at least 140 million years; Cretaceous
  • Aquatic fossils; highly divided leaves and possible floats around leaves
    • Archaefructus sinensis
  • Earliest likely woody angiosperms
• MRCA between gymnosperms and angiosperms 300mya
  • Extinct group from ~225mya: Bennettitales

Basal Lineages

• Amborella
  • Woody
  • Small reduced flowers
• Water lilies
• Star anise and its relatives
  • Woody
• No vessels

Magnoliids

• Magnolia (M. grandiflora)

Monocots

• All grasses (oats, wheats, corn, barley)
• Palm trees
• Orchids
• Pollen grain has only one opening/aperture for the pollen tube

Eudicots

• Most diverse
• Oak tree flowers (Quercus pyrenica)
• Pollen grain has or was evolved from a grain that has three openings/apertures

Reproductive Cycle

• Stigma holds pollen grain in place
• Pollen grain absorbs water
• Pollen grain tube cell takes signal; forms pollen tube
  • Going through transmitting tissue in the style, the placenta, and entering the embryo sac
• Synergids break down and emit attractive chemicals
• Pollen grain enters tube, through synergid, into egg
  • One sperm nucleus forms zygote → embryo
  • One sperm nucleus fuses with two polar nuclei of central cell → the triploid nucleus of the endosperm
• Ovary ripens into a dry or fleshy fruit
  • Dry endosperm or fleshy cotyledons inside the fruit
• Multiple pollen entering during pollination; competitive fertilization

Pollen Grain

• Wall structure has two main parts:
  • Exine: Outer structure; highly sculptured and made from sporopollenin
  • Intine: Solid continuous layer inner structure; made from cellulose
• Exine is coated with materials from the microsporangium’s tapetum

Outcrossing

• Outcrossing: Breeding between two different organisms
• Vs. Selfing
• Self-Incompatibility methods
• May also increase via
  • Differences in timing of maturation (pollen matures faster than stigma, or vice versa)
  • Dioecious vs. monoecious development
    • Foolproof

Self-Incompatibility

• Foolproof Self-Incompatibility
  • Rejection of the self’s locus/pollen
  • Controlled by alleles at the S locus
• Two forms of self-incompatibility

Gametophytic

• Easier form
• If the pollen grain’s S allele matches either the allele on the stigma or style, a pollen tube will not grow
• Haploid, single allele
• Crop plants: potato/tomato family
• GSI

Sporophytic

• If tapetum materials match the alleles on the stigma or style, the grain will not germinate
• Diploid, two alleles
• Dominant-recessive alterations
• Mustard family
• SSI

Direct Pollination

• Animal pollination
• Pollinators are rewarded by nectar and pollen; pollinator reward
  • Nectar: Sugary
  • Pollen: Proteinaceous

Pollination Syndromes

• Suites of characteristics evolved to one particular pollinator
• Hummingbirds and columbines with red petals and tubes
• Moths (Darwin)
• Beetles
• Bees and landing platform flowers
• Bats and nocturnal flowers
• Insects and rotting meat flowers

Nectar Guides

• Differences in UV reflection that signal the presence of pollen

Rate of Speciation

• Increased rates of pollination, co-evolution, etc. between pollinators and plants
• Controlling by specific characteristics: bilateral vs radial symmetry

Fruits

• Pericarp: Ovary wall and fruit around the carpal
  • Ovary wall develops into the pericarp around the seeds
• Aid in seed dispersal
  • Buoyancy in coconut fruits: Water dispersal
  • Winged fruits: dandelion seeds and maple fruits
  • Wind or animal pollination: Tumbleweed, Puncture vines
  • Ant food bodies, feces
• High effort-energy in sexual reproduction

Sexual and Asexual Reproduction

• Vegetative reproduction (Asexual reproduction): Potatoes, strawberries (stolons), Kalanchoe plantlets, aspens
• Sexual reproduction: Farther dispersal

Apomixis

• Reproduction method
• Flowers and fruits used; no fertilization
• One common method:
  • Diploid cell and a parent becoming a zygote
• Dandelion
• Non-genetically diverse offspring

Ecology

Global Ecology

• Global warming
• Biosphere

Landscape Ecology

• Larger patterns found in ecosystems
• Fire in chaparral and other habitats
• Newer area of ecology; 30-35 years

Ecosystem Ecology

• Nutrient cycling

Community Ecology

• Mutualism, predation

Population Ecology

• Breeding, evolution, intra- and inter-species interactions
• Population characteristics:
  • Populations are defined by natural or cultural geographical boundaries
  • N refers to population size (in number of individuals)
  • Population density
  • Dispersion patterns

Organismal Ecology

• Adaptations in various habitats

Areas of Population Ecology

Demography

• Population size and growth; demographics
• Births and immigration vs. deaths and emigration

Life tables

• Age-specific summaries of survival and reproduction
  • Cohort grouping: A group of individuals across age classes
  • Static grouping: Snapshots of age classes

Survivorship curves

Late Loss

• High risk at old age
• High K selection
• Humans

Early Loss

• High risk at early age
• High r selection
• High birth, seed dispersal
• Oysters

Constant Loss

• No high risk age stage
• Belding’s ground squirrel, hydra

Stair Steps

• Repeat risk stages
• Molting
• Spiders

Population Growth Models

• Omitting immigration and emigration
• Boom and bust growth
  • Logistic growth as normal; bust is the byproduct of density-independent factors
• Logistic growth
  • Density-dependent factors include territoriality (a subset of limited resources regarding space and/or mates)

Population Cycles

Life History

• All of the traits that affect an organism’s fitness
• How many times an organism reproduces in its lifetime
  • Iteroparous: Many iterations
    • May take a while to reach reproductive age
    • High likelihood of surviving for more than one year
    • Oak trees, bumper crops, insects (monarch butterfly)
  • Semelparous: Single iteration
    • Desert annuals
    • SALMON, agave: “big bang reproduction”
• Clutch/Brood Size; number of offspring produced at one time
• Age of sexual maturity/age of first reproduction
  • Earlier maturity based on life expectancy (annuals vs. perennials)
• Parental care or offspring quality and size
  • r vs. k selection
• Co-adapted traits: A suite of life history traits shared by a population

Weedy or Opportunistic Species

• Advantageous plants that compete for space by growing quickly in open areas
• r-selected species
• Semelparous
• Many young
• Small young and little parental care
• Low survival rates

Equilibrium Species

• k-selected species
• Iteroparous
• Few young
• Larger young and more parental care
• High survival rates

Life-History Continuum

• High fecundity and low survivorship vs. low fecundity and high survivorship

Metapopulation

• A population of local populations that are connected by migration
• Local populations may go extinct, but the populations are restored/repopulated via emigration from another population