Bio Midterm 3

Protist

A Eukaryote that is not an animal, plant, or fungus

Eukaryotes originated through endosymbiosis

• Nuclear membrane formed from infolding of plasma membrane

• Endosymbiosis: mitochondria and plastids such as chloroplasts were formerly small prokaryotes - engulfed by host cell

  • mitochondria and plastids have their own DNA and replicate in a way similar to bacteria

• Therefore, both plastids (e.g. chloroplasts) and mitochondria are both organelles with prokaryote-like features and DNA.

Many (but not all) protists are unicellular

• Single celled protist can be very complex, as all biological functions are carried out by organelles in each individual cell (processes carried out in subcellular organelles)

• In multicellular organisms, some biological activity is relegated to specific tissue types

Algae

• major polyphyletic group of photosynthetic protists

• Examples

  • Diatoms

  • Brown Algae

  • Dinoflagellates

  • Red Algae

  • Green Algae

Planktonic algae

Phytoplankton (e.g. diatoms)

• “phyto”: something that is plant like

• “plankton” drift in the water

Secondary Endosymbiosis

• Some algae are the result of eukaryotic heterotrophic cells engulfing autotrophic (often that host acquires photosynthetic ability) eukaryotic (already went through primary endosymbiosis) cells

  • E.g. dinoflagellates (engulfed red algae)

  • E.g. Euglena (engulfed green algae)

    • red algae and green algae already went through endosymbiosis

Protist Diversity

• Dinoflagellates have cellulose cell walls

• Both unicellular and multicellular

• Flagellum in groove (cell spins as it moves)

• Many are photosynthetic (phytoplankton): secondary endosymbiosis

Dinoflagellate blooms cause ‘red tides’

A red tide, often toxic algal bloom

Diatoms and brown algae are both…

Stramenopiles

• Have two dif kinds of flagella in certain life stages

• some stramenopiles are algae but not all

Diatoms

• Protists: algae, stramenopiles

• Glass-like cell walls of silica

• unicellular

• photosynthetic phytoplankton

• extremely abundant: important for CO2 absorption in the oceans

Brown algae

• Brown algae are closely related to diatoms (similar flagellum - both stramenopiles)

• Often large, multicellular algae, attached to the bottom of ocean: kelp forests

Red algae

• Red algae have additional pigments that give them red color, or dark reddish-brown

• Multicellular or unicellular

• Often found much deeper in the sea than green and brown algae

• Closely related to green algae (but not brown algae)

• Sushi ‘wrapping’ sea weeds are usually red algae

Green algae

• Green algae have bright green chloroplasts

• Multicellular or unicellular

• Closely related to true plants (land plants)

• E.g. Chlorophytes (such as ‘sea lettuce’ and Volvox) and charophytes

Some protists are…

mixotrophs: they can switch between autotrophy and heterotrophy (their source of carbon) or photosynthetic vs chemosynthetic (source of energy)

• Example: Euglena

  • can switch its photosynthetic processes on and off (common in freshwater)

  • I think it can also switch its source of carbon

Examples of protist parasites

• Trypanosoma

  • an example of a parasitic protist genus: sleeping sickness in humans

  • Related to Euglena (both are Euglenozoans)

    • long, torpedo shaped cell

  • Infects bloodstream and nervous system (into the nervous tissue), disrupts sleep cycle

  • Vector (spreads through the): tsetse fly (Africa)

• Plasmodium

  • another example of a parasitic protist genus (malaria)

  • Infects and lyses red blood cells

    • goes into the blood cells (notably red blood cells) and multiplies inside the cells

  • Vector: mosquitoes

  • Has historically killed millions

  • Causes symptoms of fever, sweating, and chills

Lifecycle of Plasmodium (the parasite that causes malaria)

• protist parasite

• Formation of gametes, fertilization and meiosis happen within the mosquito

• Most life stages are haploid

• Mosquito bites: immature Plasmodium infects liver first, and matures

• Second infective stage is in red blood cells (RBCs)

• Mosquito ingests gametocytes, that can produce gametes

Unikonta

• Most phylogenies of Eukaryotes find a monophyletic group (“Unikonta”) that contains many protist groups (notably ameobozoans), but also animals and fungi

• Amoebozoans include slime molds and various amoebae

Amoebozoans

• Eukaryotes: Unikonta: Protists (although not all protists are unikonta - polyphyletic) : Amoebozoans

• Amoebae are unicellular heterotrophs

• engulf food particles (e.g. bacteria) by phagocytosis (change shape of cell and stretch out to engulf food)

• Move by using pseudopodia projecting from the cell

• Amoebozoans include slime molds and various amoebae

Which disease is caused by a protist?

• AIDS

• Malaria

• Syphiis

• Kuru

Malaria (plasmodium)

Which one is an alga?

• Amoeba

• Trypanosoma

• Plasmodium

• Diatom

Diatom

Slime molds

• Eukaryotes: Unikonta: Protists (although not all protists are unikonta - polyphyletic) : Amoebozoans: slime molds

• Scientific name: mycetozoans (“fungus animals”)

  • once thought to be fungi

• terrestrial but usually need a lot of moisture

• fruiting bodies with sporangia (a bit fungus-like)

• Two main branches:

  • Plasmodial slime molds

  • Cellular slime molds

Plasmodial Slime Molds

• Eukaryotes: Unikonta: Protists (although not all protists are unikonta - polyphyletic): Amoebozoans: slime molds": plasmodial slime molds

• NOT “plasmodium” which causes malaria

• Complex life cycle, main stage = plasmodium: large cytoplasm is undivided by membranes and contains many diploid (2n) nuclei.

  • This plasmodial stage grows (and moves) on decomposing material, engulfing bacteria and other organic material by phagocytosis.

• Unicellular

Cellular Slime Molds

• Eukaryotes: Unikonta: Protists (although not all protists are unikonta - polyphyletic): Amoebozoans: slime molds": cellular slime molds

• Microscopic to barely visible (fruiting bodies often found about 1 mm.)

• Very common in soil around the world

• Used as an experimental model for studying the evolution of multicellularity.

• The feeding stage of the life cycle consists of solitary cells (haploid amoebae) mainly feeding on bacteria (phagocytosis I think)

  • When food is depleted, the cells form a multicellular aggregate “slug” that functions as a unit

  • Cells are still separated by their membranes

• Fruiting bodies with sporangia

Life Cycle of Cellular Slime Molds (probably dont need to know)

• Eukaryotes: Unikonta: Protists (although not all protists are unikonta - polyphyletic): Amoebozoans: slime molds": cellular slime molds

Asexual reproduction (haploid the whole time):

• The mass of aggregated amoebas forms fruiting bodies and spores (in the spore head at the top).

• Spores disperse and become emerging amoeba (in favorable environmental conditions).

• emerging amoeba hatch to become solitary amoebas

  • Solitary amoebas reminder: The feeding stage of the life cycle consists of solitary cells (haploid amoebae) mainly feeding on bacteria (phagocytosis I think)

Sexual reproduction:

• Sometimes they enter into sexual reproduction

• Fertilization: two haploid amoeba fuse to form a diploid zygote

• Go through meiosis to produce haploid amoebas (solitary amoebas)

most of what we see of fungi are the fruiting bodies

• mushrooms, truffles, the fruiting bodies of mold (what we see)

Eukarya: Kingdom of Fungi

• Fungus = Lat: “mushroom”

• Mycology = the science of fungi

• Fungi are diverse and widespread. Perhaps 100,000 described spp. (estimatied > 1.5 million species total).

• Includes molds, yeasts, as well as fungi in soil, forming mushrooms, puffballs, truffles, etc.

• Eukaryotes (true nucleus and other organelles present), but neither plant nor animal nor protist

  • Previously often mixed up with plants; but no chlorophyll and actually closer to animals

  • Heterotrophic

    • Get nutrients by absorbing from surroundings

• Fungi generally require moisture and organic material

  • most require oxygen, though some are facultative anaerobes (makes energy (ATP) using oxygen via aerobic respiration when it is present, but can switch to fermentation or anaerobic respiration when oxygen is absent)

    • e.g. the yeast Saccharomyces cerevisiae

Evolution of Fungi

• Fungi: kingdom eukaryotic organisms separate from protists, plants, or animals

• Relationships: fungi are actually more closely related to animals, and amoebozoans than to plants

• Belong in a (probably monophyletic) group together with animals and amoebozoans

Importance of fungi

• Essential decomposers for ecosystems. Fungi decompose dead organisms, fallen leaves, and other organic materials.

• Recycle vital chemical elements back to the environment in forms other organisms can assimilate (take in)

• Able to break down hard to digest materials such as cellulose

  • Insects can’t digest cellulose directly - but fungi can

  • Termites, and some ants, grow “fungus gardens” on cellulose inside their communities

• Plants often depend on mutualistic fungi to survive

• Humans cultivate fungi for food, antibiotics (some fungi produce antibacterial chemicals) and other drugs, to make bread rise, and to ferment beer and wine. Also, model organisms for lab studies.

The characteristics (body structure) of Fungi

• Body forms

  • Most species are multicellular: form extensive mycelium (big network of threads) which produce fruiting bodies (e.g. mushrooms)

    • filamentous tube-like strands that make up mycelium are called hyphae (sing. hypha)

      • mycelium = aggregate of hyphae

    • Spores serve in reproduction

      • can be very resistant e.g. overwintering or drought

      • Mushroom shape is to specifically help spread spores in the air.

  • Some are unicellular

    • yeasts

Fungi lifestyle (obtain nutrition, roles)

• Fungi are heterotrophs (but they don’t ingest food)

  • Obtain nutrition by absorption (through the cell walls)

• Diverse lifestyles (Note: categories are not mutually exclusive)

  • Most are decomposers (saprophytes) - feed on dead tissues or organic waste

  • Some are parasites

    • Absorb nutrients from a living host

    • Responsible for most plant diseases (also some human diseases)

  • Mutualistic symbionts - mutually beneficial relationship between a fungus and another organism

    • Root tip fungi and plants - fungi help in nutrient absorption and receive energy and nutrients from the plant (more later)

Fungi produce a wide variety of interesting chemicals

• Powerful enzymes break down dead (sometimes living) tissues

• Antibiotics - get rid of competition (kill bacteria that is competing for its same resources), major importance to medicine

• Other drugs - including hallucinogens

  • Fly agaric (Amanita muscaria)

• Toxins - sometimes highly potent

• Metabolic byproducts include alcohol (ethanol, used in brewing) and CO2 (used in baking)

Toxic fungi

• typically produce chemicals that destroy the liver and kidneys

• E.g. death cap (Amanita phalloides), destroying angel (Amanita virosa)

Bioluminescence in Fungi

Probable function: attracting insects that spread spores

Hyphae

• Tough cell walls composed of chitin (polysaccharide)

  • Grow at tips, branch extensively

    • Mycelium

  • Cell (with nucleus) in hyphal tip

  • Secrete enzymes (exoenzymes) breaking down complex molecules

  • Products (nutrients) absorbed by hyphae

Four specific fungal forms

• molds, yeasts, lichens, and mycorrhizae, have evolved morphological and ecological adaptations for specialized ways of life

  • These have evolved similarly (but independently) in several groups of fungi

Molds

• A mold is a rapidly growing, multicellular, asexually reproducing fungus.

  • The mycelia of these fungi grow as decomposers or parasites on a variety of substrates

  • Produce asexsual spores (some molds can also reproduce sexually)

Mycelia

Google: the root-like, vegetative network of a fungus made up of branching, thread-like structures called hyphae.

Yeast

Unicellular fungi that inhabit liquid or moist habitats, including plant sap and animal tissues.

• Most yeasts reproduce asexually by simple cell division or budding off a parent cell.

  • e.g. saccharomyces (used in baking + brewing) “sugar fungus”

• Some yeasts also reproduce sexually.

Lichens

• a symbiotic association (partnership) of photosynthetic microorganisms (either green algae or cyanobacteria (blue-green algae)) in a mesh of fungal hyphae.

  • Fungus - provides structure, protection, absorption

  • Alga or cyanobacterium - provides photosynthesis (nutrients)

  • E.g. “reindeer moss” - a shrub-like species of lichen

• A lichen is classified as single species, even though it’s two organisms in one

• Lichens are nature’s biological monitors of pollution and air quality

  • Many species very sensitive to pollution (which species are present can indicate air quality)

    • They grow slowly and tend to build up whats in the air

  • More resistant species can also be analyzed (measured) for pollutants, including bioaccumulation of heavy metals and radioactive isotopes

Mycorrhizae (symbiosis)

• Definition: symbiotic (generally mutualistic) association between a fungus and the roots of a vascular plant.

• Mycorrhiza: “Fungus root”

• Mutualism btw:

  • Fungus: provides water, nutrients such as phosphates and some protection from root disease

  • Plant root: provides carbohydrate for fungus

• Extremely important ecological role of fungi! The majority of plant species have mycorrhizal fungi (80% of plants get phosphates and other minerals from such symbionts)

• Plant growth without mycorrhizae is often stunted.

• Mycorrhizae may have been important to the colonization of land by plants (even before roots had evolved)

  • Genetic evidence - all major groups of plants have genes that code for recognition of symbiotic fungi (shows that the ability to partner with fungi is an ancient trait)

  • Fossil evidence - early fossil plants associated with structures similar to mycorrhizae.

Examples of fungal groups (based on relationship - phylogenetic - rather than analogous traits)

• Chytrids

• Mucoromycetes

• Ascomycetes

• Basidiomycetes

Chytrids (Chytridiomycota)

• Fairly primitive

• Flagellum on spores

• Mostly aquatic: often found in lakes and in moist soil

• Some cause infectious disease in animals (e.g. in frogs)

Mucoromycetes

• Round sporangia (zygosporangium) often sit on long strands of hyphae

• Many molds belong to this group

• Some species can cause serious disease in humans

• Some have coencytic mycelium (many nuclei, no cell walls in between) and are specialized for mycorrhizae.

Ascomycetes (Ascomycota)

• “Sac fungi”

• Have microscopic sacs producing spores

• Very widespread, land, lakes, oceans

• Some species form lichens; together with algae

• Also include morels, cup fungus, many yeasts etc.

• E.g. Truffles are the subterranean fruiting bodies of certain species of ascomycetes

  • Smell delicious to many animals → digging them up results in spreading spores.

Basidiomycetes (Basidiomycota)

• “Club fungi”: spores on little club-like protrusions called basidia

• Long-lived heterokaryotic (dikaryotic) stage (fused cell walls but two separate nuclei)

• Prominent fruiting bodies such as mushrooms or puffballs

• Also include some plant parasites (plant diseases), such as rusts

• Important in decomposing decaying wood, also often form mycorrhizae

Fungus reproduction and life cycle (basidiomycete example)

Sexual reproduction:

• Stages: Haploid (n), diploid (2n), and dikaryotic (i.e. n+n)

• Fruiting bodies produce haploid (1 set of chromosomes) spores through meiosis.

• Spore give rise to haploid mycelia mating types +/-

• These mycelia unite (a + mycelium with a - mycelium) and produce dikaryotic mycelium and dikaryotic fruiting bodies

• Fusion of nuclei (to become diploid - 2n) (short diploid stage), then meiosis produce new spores (n)

Note: many fungi can also reproduce asexually

Fungi as parasites + pathogens: Plants

• About 30% of the 100,000 known species of fungi are parasites, mostly on or in plants

• Invasive ascomycetes have had large infestations on forest trees, such as American elms and American chestnut

• Some basidiomycetes form bracket fungi (conks) on trees

• Other fungi, such as rusts infect grain crops, causing large economic losses each year.

Fungi as parasites + pathogens: Humans (and other animals)

• Yeast infections of the vagina

• “Ringworms”

• Athlete’s foot

• Valley fever - bronchitis-like or flu-like symptoms → infects your lungs

Dikaryotic

2 nuclei / heterokaryotic

Plants (Kingdom Plantae)

• related to green algae (470 mya.)

  • Among green algae, the charophytes are especially plant-like (e.g. genus Chara lives in fresh water)

• Gradually evolving from an organism similar to Chara, true land plants adapted to the dryness of land:

  • waxy cuticle on the epidermis retains moisture

  • differently organized cellulose fibers support an upright structure

  • stomata exchange gases with the air

  • roots get resources from the soil

• reproduction also changed (resistant spores, seeds (i think to avoid drying out))

Plant life cycle

• Fertilization creates a zygote (single diploid cell)

• Mitosis and development creates a sporophyte (multicellular + diploid)

  • over time the sporophyte stage has become more dominant

  • sporophytes produce spores

• Sporophyte undergoes meiosis to produce haploid spores

• Mitosis and development creates a gametophyte (multicellular + haploid)

  • gametophyte produces gametes (through mitosis)

• Spores - many plants have two kinds:

  • megaspores (germinate (grows into a) → female gametophyte)

  • microspores (becomes a male gametophyte)

True plants (3 main groups)

• Nonvascular plants (no vascular tissues - can’t grow very tall)

• Seedless vascular plants

• Seed plants (monophyletic, also vascular plants)

Nonvascular plants (bryophytes)

• Include mosses and similar plants (e.g. liverworts and hornworts)

• Probably paraphyletic

• Gametophyte (n) is dominant (google: the haploid stage is the main, longest-lived, and most visible part of the organism)

• Probably similar to earliest land plants 470mya

• No vascular tissue or stomata - need moist habitat (a few species can handle desiccation (no water))

• Common in moist forest and boggy areas - build up layers of peat

• Sperm cells swim through water from male gametophyte to the female gametophyte (sometime on same plant)

• Sporophyte spreads spores into the air

Seedless vascular plants

• Include club mosses, ferns, and horsetails (paraphyletic)

• True vascular tissue

• Gametophyte is small

• Sporophyte (2n) is dominant

• Reproduction is similar to mosses - disperse by the use of spores

• In the Carboniferous Period (ended 300mya) seedless vascular plants were dominant on land

• Club mosses + ferns grew to large size; whole forests of club moss trees

• These enormous organic deposits turned to coal over time

Seed Plants

• Include most of the plants in our daily environments (e.g. from large trees such as conifers, to small shrubs and flowering herbs)

• Small (almost microscopic) gametophyte (n) (developed from a spore on the plant), sporophyte (2n) is dominant, has vascular tissue (can grow to large sizes)

• Male gametophyte (n) is the pollen grain, fertilizes egg in female gametophyte (less need for moisture)

• Female gametophyte sits within the ovule, which becomes the seed (package with plant embryo inside and some nutrients)

• Disperse by the use of seeds (embryo inside)

• Two main groups: Gymnosperms and angiosperms

• Gymnosperms generally use wind pollination, while angiosperms typically have flowers that attract insects.

Gymnosperms

• Seed Plants: Gymnosperms

• “naked seed” - seeds aren’t covered by a fruit (produced by a cone that opens up → seed is naked)

• Mainly conifers, also include a few other groups e.g. cycads and genus Ginkgo (fan like leaves)

• Wind pollination

Conifers

• Seed plants: Gymnosperms: Conifers

• Conifers

  • Include e.g. pines, firs, redwoods

  • Very large forests, particularly in the Northern Hemisphere

  • Leaves are needles

  • Produce male and female cones (pollen cones, ovulate cones)

  • Male gametophyte (develops from microspores) - pollen grain produced inside of the pollen cone

  • Female gametophyte (develops from megaspore) - sits inside of the ovule (which becomes seed) inside ovulate cone

  • Redwoods (Sequoioideae)

  • Bristlecone pine trees

Redwoods

• Seed Plants: Gymnosperms: Conifers: Redwoods

• The largest trees and perhaps the largest organisms, long-lived (more than 2000 years)

• Two species in California: coast redwood + giant sequoia +1 smaller species in china (Dawn redwood)

• Reddish brown wood and bark

Coast redwood (Sequoia sempervirens)

• Seed plants: Gymnosperms: Conifers: Redwoods: Coast Redwood

• The world’s tallest tree, 115m (379ft). Second largest tree by volume.

• Numerous small ovulate cones

• Coast lowlands of Northern California (Oregon)

• forests possibly highest biomass/yr production; - only about 5% remains intact.

  • pretty good at absorbing CO2 (bc that is how tissue is built - CO2 absorbed → photosynthesis etc)

Giant sequoia (Sequoiadendron giganteum)

• Seed plants: Gymnosperms: conifers: redwoods: giant sequoia

• The biggest tree by volume

• Medium size ovulate cones

• Up to 3500 years old

• Sierra Nevada

• Adaptations to frequent fires:

  • Extremely thick bark, relatively fire resistant

  • Cones usually open and release seeds after fires

  • Some fires are needed to get young giant sequoias

Bristlecone pine trees

• Seed plants: gymnosperms: conifer: bristlecone pine

• Can live for 5000 years

• High altitudes in California and Nevada

• among the oldest living organisms

Gymnosperm life cycle

• Seed plant: gymnosperm

• The dominant stage (the majority of the mass of the tree) is the diploid (2n) sporophyte stage

• Male gametophyte (n) is the pollen grain (develops form microspore) in pollen cone

• Pollen is dispersed to ovulate cones through wind

• Ovulate cone: contains ovules - the megaspore develops within ovule to become female gametophyte (n) → which produces an egg

• Pollen fertilizes through pollen tube

• Embryo (2n) develops within ovule which becomes the seed

• The embryo is surrounded by haploid food reserves in the seed.

Angiosperms (flowering plants)

• Seed Plants: Angiosperms

• Male gametophyte - pollen grain develops from microspore inside of the anthers (in flower)

• Female gametophyte develops from megaspore inside of the ovule, which is inside the flowers ovary (becomes the fruit)

• Two groups of angiosperms: monocots + eudicots (dicots)

  • One (monocot) or two (eudicot) seed leaves (cotyledons)

• Flowers are designed for pollination by attracting insects

  • Nectar in flower, plus color and shape of petals attract insects

  • Pollen produced in the anther (male part of flower) grows a pollen tube when landing on stigma

  • Ovule will become the seed, and ovary the fruit

  • Fruits vary a lot in structure

• Most stages are similar to gymnosperms, but:

  • Pollen transfered to the stigma of the flower

  • Pollen then produces a pollen tube and two sperm cells

  • Double fertilization (zygote, endosperm in seed)

What is double fertilization?

• in Angiosperms (part of seed plants)

• Egg is fertilized by the sperm from the pollen tube and produces a diploid zygote (2n) (zygote = cell formed by union of sperm and egg cells)

• Seperately, the other sperm cell fertilizes the central cell nuclei, these fuse and become triploid (3n) endosperm (ppl dont rly know why) = nutrient within the seed

• The ovule (which holds the egg) becomes the seed, holding/including endosperm and embryo (2n)

Differences between monocots and eudicots

• Seed plants: angiosperms: monocots + eudicots

• One (monocot) or two (eudicot) seed leaves (cotyledons)

• Veins (parallel in monocots but branching in eudicots)

• Vascular bundles (vascular tissue in the stem is random in monocots but grow in circles in eudicots)

• Flowers/petal numbers (multiples of three in monocots, multiples of four of five in eudicots)

• Roots (monocots have fibrous roots)

  • but not the best way to differentiate bc roots look so dif anyway when grown in desert vs forest etc.

Eudicot examples

• Seed plant: angiosperm: eudicot

• roses, poppies, apple trees

• Oaks: Much of California is relatively dry, dominated by oak savanna, grasslands with scattered oaks

• The fruit of an oak is the acorn. Chemicals that make them inedible gradually degrade so animals often store acorns.

• Many trees are deciduous, (falling off) recycling nutrients from the leaves (roots reabsorb) and dropping them in winter e.g. valley oak

• Others are evergreen e.g. coast live oak (retain their leaves)

Monocot examples

• Seed plants: angiosperms: monocots

• Lilies, palm trees, grasses (e.g. bamboo)

• Many of our most important grains are grasses (e.g. wheat, barley, rice, rye, maize)

Vascular plant anatomy

1. a shoot system

• includes stems and leaves (main photosynthetic organ), and reproductive organs (such as flowers). Absorb CO2 and light, produce carbohydrates (sugars etc.)

• shoots rely on water and minerals absorbed by the root system

2. a root system

• plants take up water and minerals from the soil

• roots rely on sugar produced by photosynthesis in the shoot system.

Shoot system

• Vascular plant anatomy

• Leaves

  • The leaf is the main photosynthetic organ of most vascular plants

  • Leaves generally consist of a flattened blade and a petiole which joins the leaf to the stem

  • Leaves usually have stomata underneath (small openings for gas exchange of CO2 and O2 in photosynthesis)

    • Stomata control transpiration

      • guard cells (on either side of the stoma) control the amount of water evaporation by opening or closing

      • Turgidity from water pressure controlled by ion transportation and osmosis.

      • As water is inside it opens up, water leaves it closes

      • a way to contradict desiccation (drying out)

Root system

• Vascular plant anatomy

• A root is an organ with important functions:

  • anchoring the plant

  • Absorbing minerals and water (occurs in the root hairs, increase the surface area)

  • Usually connected to mycorrhizae

  • Storing carbohydrates

  • Note: carrots and sweet potatoes are roots, but potatoes are stem tubers (not roots))

Primary Growth of Shoots and Roots

• Vascular plant anatomy

• An apical meristem is a dome-shaped mass of dividing cells at the shoot or root tip

• A root cap protects the root apical meristem

• Cell division and specialization of meristem cells lengthens shoots and give rise to plant organs (e.g. leaves)

All vascular plants have three tissue systems

• Dermal tissue system - epidermis (made of epidermal cells) with waxy cuticle - in woody pants supplanted (replaced) by a thick layer of cork and cork cambium (layer of actively dividing plant stem cells - role to produce new outer armor - pushing out layers of cork (make up part of the bark)) in the bark

• Vascular tissue system - phloem and xylem, often in vascular bundles

• Ground tissue system - photosynthesis, storage and support - often subdivided into cortex (close to epidermis) or pith (center of the stem)

• Tissues are differently oriented in roots

  • Vascular tissue at the core, then cortex (ground tissue), and epidermis on the outside

  • Root hairs are dermal tissue (epidermal)

Phloem

one of two major components of vascular tissue (in vascular plants)

• Living cells with sieve plates at the ends, plus supporting cells around.

• Transport sugary water, other organic materials

Xylem

one of two major components of vascular tissue (in vascular plants)

• Consists of dead tube-like cells that transmit water and minerals

• Found in all parts of the plant. Wood is almost pure xylem.

Secondary Growth of wood

• Vascular plants

• A lateral meristem consists of a vascular cambium and cork cambium (these are cylindrical in shape and consists of dividing cells (producing new cells) along the stem and root)

• The vascular cambium lays down (creates) secondary xylem (wood) to the inside and secondary phloem to the outside

• The cork cambium layer (derived/originated from secondary phloem) produces cork

• Bark is the cork layer together with the phloem and the cork cambium

• In a section through a wooden stem, the living cells are the vascular cambium, secondary phloem, and cork cambium.

• Wood (secondary xylem) is cellulose fibers (strong structure) in a matrix (surrounding glue) of lignin (which is cross linked hydrocarbon rings bound to carbohydrates)

  • strong structural support for larger plants

• Sapwood consists of newer layers of wood that are actively transporting xylem sap

  • very important for the transport of water

  • sapwood eventually transforms to heartwood as the tree grows (just fills up with resin)

• Heartwood consists of older layers of wood that are infused with resins to protect from e.g. fungal infection (mainly structural)

Xylem and phloem transport

• Vascular plants

• Xylem sap movement is pulled by transpiration (loss of water through evaporation)

• Water molecules stick to each other (hydrogen bonds) and move up through the plant through the xylem

• In addition plants also pump ions from soil into xylem, creating root pressure

• Sugary water in phloem, phloem sap, can move both up and down the plant from sugar sources to sugar sinks (part diffusion, part active transport)

Coast redwoods (another method of water uptake?)

• absorb water from fog

Importance of bark

• Protective (fire, damage, infection etc.)

• contains vital phloem

• A tree needs a continuous connection of bark to live, can survive as long as there is continuous connection of bark from root to shoot

  • can’t cut a horizontal ring of bark off

Natural gums and resins (not the most important thing)

• fluids produced by plants to protect in areas where they have been cut or damaged and to prevent against infection

• Gums: contains hydrophilic polysaccharides (milky emulsion) often produced by angiosperm trees. Dry solid by evaporation of water

  • generally easier to extract from angiosperms

• Resins: contains hydrophobic hydrocarbons (such as terpenes and terpenoids: “turpentine”), resin can harden over time (fossilize) and become amber.

  • generally easier to extract from gymnosperms

• Uses: Latex are mixes of gums and resins, gum arabic for watercolors and medicine (pills), ___

Plants depend on bacterial and fungal symbionts

• The Earth’s atmosphere consists of about 80% nitrogen (N2)

• However, nitrogen deficiency is the most common nutritional problem in plants (amino acids, nucleic acids, etc.)

• Plants cannot absorb nitrogen directly from the air

  • Nitrogen fixing bacteria convert N2 (nitrogen gas) to ammonia (NH3), which can be absorbed (as ammonium ions, converted to aminoi acids, etc.)

  • Some plants (e.g. legumes such as beans, peanuts) have mutualistic Rhizobium bacteria in nodules of the roots. The bacterium provides NH3, while the plant supplies sugars

  • Nitorgen fixing bacteria thus help to supply nitrogen into the nitrogen cycle (circulation of nitrogen between organisms and environment)

• Fungal mycorrhizae supply minerals, phosphate, stimulate root growth, make antibiotics to protect against plant pathogens.

  • also helps to fight off other fungi (?)

Asexual reproduction in plants

• Asexual reproduction is also called vegetative propagation (new plants grow from parts of the old ones), and the resulting asexually produced offspring, often called a clone, is genetically identical to its single parent.

• Asexual reproduction in many plants is an extension of their capacity to grow throughout life.

• Example: redwoods in a circle often stem from a “parent” root system of a felled tree

• Example: Asexual reproduction in willows

  • can also do sexual reproduction

  • Willows have relatively brittle new shoots

    • These often break off and fall into a stream

    • Set down a root system at the bank and develop into a new tree

Variations of plant growth and nutrition

• Epiphytes grow on other plants but are not really parasites (e.g. orchids)

• Parasitic plants tap into host plant vascular tissue. Absorb sugar, water, minerals. E.g. mistletoe.

• Indian pipe (ghost plant) is unusual in that it is a parasite on mychorrizal fungi (fungus is connected to plants near by obtaining sugar and the Indian pipe is stealing it from the fungus)

• Carnivorous plants:

  • Nitrogen-poor soil - so this is the primary way the plant obtains nitrogen

  • Trap small animals (mostly insects) and produce enzymes to digest them

Animals: Kingdom Animalia, or Metazoa

• Animals = closest protist relatives: choanoflagellates

• General characteristics (all animals)

  • multicellular eukaryotes

  • have Hox genes

  • cells lack cell walls (unlike plants and fungi), but often reinforced with protein fibers (connecting cells to each other and for protection)

  • heterotrophic (unlike autotrophic plants) - always have to obtain organic molecules from other organisms

  • obtain nutrients by ingestion (unlike fungi)

• General characteristics (most animals)

  • sexual reproduction

    • male: produces haploid motile sperm

    • female: produces haploid immobile egg cell

  • have true tissues (exception: sponges)

  • tissues are derived from 3 germ layers: ectoderm, mesoderm, endoderm (exception: sponges, cnidarians)

  • highly mobile (nervous system, muscular system; exception: sponges and few others)

Typical/generalized animal life cycle (example: echinoderm)

• a small flagellated (motile) haploid sperm fertilizes a larger, haploid, nonmotile polarized egg.

  • Forms diploid zygote

• Mitotic cell divisions lead to the formation of the hollow blastula (mammals: blastocyst)

• Gastrulation (reorganizing) leads to the formation of a gastrula with 3 germ layers (ectoderm, endoderm, mesoderm)

• Tissues continue to differentiate, eventually forming the adult animal. Specialized gonads (testes, ovaries) in the body then produce new haploid gametes (sperm, egg (through meiosis)

General body structure found in most animals including humans (not sponges, cnidarians)

• Three germ layers - ectoderm, mesoderm, endoderm, and many animals have a coelom (body cavity)

  • Digestive tract (from endoderm)

  • Gaps in mesoderm = coelom

  • Muscles etc. (from mesoderm

  • Body covering (from ectoderm)

    

Some animals undergo metamorphosis (Larva → adult)

• Some animals have a gradual development form juvenile to adult (e.g. mammals)

• Other animals have a distinct larval stage, which is radically different from the adult - different anatomy, metabolism, eating different food etc.

• Life cycles of many insects, amphibians etc. include a metamorphosis, during which the animal takes on different body forms as it develops from larva to adult

• Example: butterflies and beetles

Type of symmetry in animals

• Animals can be categorized according to body symmetry (or lack of it)

• In general - symmetry fits lifestyle

• Animals (except sponges) either have radial or bilateral symmetry

  • Radial symmetry: have a top and bottom but lack back and front or R and L sides

    • either don’t move or move very slowly

  • Bilateral symmetry have mirror-image right and left sides and front (anterior) vs back (posterior)

    • tend to have a more active lifestyle (sensory systems for the most part go at the front because thats where they encounter things first)

Animal Phyla: we will cover some important invertebrate phyla + chordates which include vertebrates

• Animal phyla: radically different body plans “bauplan”

• Invertebrates: a paraphyletic taxon - animals without vertebral column (backbone)

  • Phylum Porifera (Sponges)

  • Phylum Cnidaria

  • Bilaterians

Choanocytes (cyte = ?)

cell

Phylum Porifera (Sponges)

• Very primitive (protist-like)

• No symmetry

• No true tissues

• Suspension feeders (filter feeders) obtain food particles from water

• Sponge anatomy: a highly porous structure

  • Have protist-like cells: e.g. Collar cells (choanocytes (cyte = cell)): create a water current through sponge. Resemble choanoflagellate cells

  • Amoebocytes: amoeba-like cells create spicules and protein fibers.

  • Spicules: structural “skeletal” elements found in most sponges that provide ___

  • 
    

Phylum Cnidaria

• Cnidarians are radially symmetrical carnivores (marine or fresh water) with a simple gastrovascular cavity, and only two germ layers

  • Two basic forms: polyp or medusa (some go through both stages, but usually one is dominant)

  • Cnidocytes are unique venomous stinging cells that capture prey and function in defense.

  • Include sea anemone (cnidarian ployp) and jellyfish (cnidarian medusa)

• Corals are colonial cnidarians

  • build up over many years

  • usually have a symbiotic relationship with algae

• Some cnidarians have extremely toxic cindocytes

  • e.g. sea wasp, portuguese man-of-war

Bilaterians

• The rest of the animal phyla are Bilateria

• Most Bilaterians have bilateral symmetry (except echinoderms - which lost the trait), and all have three germ layers (endoderm, mesoderm, ectoderm)

• Bilaterians

  • Protostomes: Spiral cleavage. The first opening to occur during gastrulation becomes mouth

    • E.g. arthropods, molluscs

  • Deuterostomes: Radial cleavage. The first opening becomes anus

  • E.g. echinoderms, also chordates and vertebrates.

Flatworms (Phylum Platyhelminthes): the simplest bilateral animals

• Flatworms are the most primitive bilaterians

• 3 germ layers, but no coelom

• Live in marine, freshwater, and damp terrestrial habitats, eating various organic materials (e.g. algae, bacteria)

• Some are parasitic (e.g. tape worms)

• Many flatworms (e.g. the black planarian, a freshwater sp.) have the ability to regenerate the entire body from a small piece

  • Cut in half, it will regenerate into two flatworms

  • This is due to the entire body containing stem cells within the tissues

  • Sometimes reproduce asexually by pinching themselves in half

Phylum Mollusca

• Animal phylum

• Over 100,000 spp.

• Very numerous in the oceans, also in fresh water. Some species on land.

• Anatomy varied, but with important underlying similarities

  • Soft-bodies (but often with a hard shell)(probably ancestor had a shell)

  • Muscular foot

  • Muscular mantle, and mantle cavity (usually with gills inside)

  • Many have a radula (rasping tongue)

• Missed a slide

• Mollusks are important predators, filter feeders, and herbivores

• They are a very important food sources for other animals (e.g. sperm whale eating giant squid)

• Also a major food source for humans (e.g. oysters, calamari, snails)

Mollusk Taxonomy - example classes:

• Chitons

  • Common in oceans along shores

    • close to primitive mollusk body plan

    • shell consists of eight plates, large foot

    • eat algae using radula

• Gastropods

  • The largest group of mollusks; snails and slugs

    • Found in fresh water, marine, and terrestrial environments

    • the only mollusks that have species on land. Terrestrial spp. use the mantle cavity as a “lung”

    • often protected by a single, spiral shell (slugs have lost their shell).

    • Herbivores or predators

• Bivalves

  • Include clams, oysters, mussels, scallops

  • Have shells divided into two halves that are hinged together. The shells are placed on the sides (laterally)

  • Bivalves are suspension feeders

  • Many can move using the foot

  • Sometimes attached to teh substrate by strong threads

• Cephalopods

  • Fast, agile predators

  • Muscular foot modified into arms/tentacles witih suckers

  • Mantle functions in “jet propulsion” (draw water in and squirt it out to propell)

  • Relatively complex brains

  • Well-developed eyes

  • Shell is large in a nautilus, small and internal in a squid and cuttlefish, missing in octopus.

  • Many can change colors rapidly

  • Many can squirt ink (defense)

  • Squid and cuttlefish are fast-swimming, streamlined predators

  • Octopuses: active predators on or near the seafloor.

  • Giant squid and colossal squid are the largest invertebrates (up to 46ft)

Toxic Mollusks

• Bivalves sometimes accumulate poisonous algae

• Some mollusks can deliver a deadly sting/bite (e.g. cone snail + blue ringed octopus)

Phylum Annelida: The segmented worms

• Annelids have segmentation, the subdivision of the body along its length into a series of repeated parts

• Most are hermaphrodites

• Annelids are found in damp soil, the sea, and most freshwater habitats.

• Examples

  • Earthworms ingest soil and extract nutrients, aerating soil and improving its texture

  • Ragworms have appendages with stiff bristles or chaetae. Active predators.

  • Tube worms are filter-feeders in the sea

  • Leeches are free-living carnivores; or blood suckers.

    • Have suckers on each end

    • Blood-sucking leeches use razor-like mouth parts, secrete an anesthetic and an anticoagulant.

Phylum Nematoda

• Nematodes or roundworms (phylum Nematoda) are abundant and diverse, with thousands of species (25,000 - 500,000?)

  • Very simple bilateral symmetric structure

  • three tissue layers, and pseudocoelom body cavity (not a “true” coelom)

  • Moist habitats: most eat bacteria, decomposing matter, but some are parasites (e.g. Guinea worm and Trichinella)

Phylum Arthropoda

• by far the most abundant animal phylum - well over 1 million insects (within arthropods)

• Insects = largest subgroup

• Most closely related sister taxon: velvet worms (Onychophora; not true arthropods)

• Arthropods have

  • an open circulatory system - hemolymph (not blood) pumped from heart through short vessels then to spaces surrounding organs

  • an exoskeleton of chitin (external skeleton that is periodically molted to permit growth), sometimes reinforced with calcium carbonate (crustraceans)

  • Jointed appendages - most are legs, but some of these hae become modified to other functions e.g. mouth parts

  • Some still have similar and repeated body segments, but today man have distinct body segments; head, thorax, abdomen

  • many have compound eyes

Groups of Arthropods

• Crustaceans (multicrustacea)

• Arachnids

• Myriapods

• Insects