Protists and Endosymbiosis Theory

• The endosymbiosis theory proposes that mitochondria and chloroplasts in eukaryotic cells originated as separate prokaryotic microbes.
• A bacterium engulfs another bacterium, which then lives inside the other.
• Both bacteria benefit from the arrangement in endosymbiosis.
• The internal bacterium is passed on from generation to generation.

Characteristics of Protists

• Protists are eukaryotic, being the first to have a nucleus.
• Protists appeared approximately 1.5 billion years ago.
• The majority of protists are unicellular, but some are multicellular.
• Protists mostly live in water (marine, freshwater), moist areas (soil) .
• Some protists can even live inside the human body (blood).
• Most protists reproduce asexually (binary fission), while some reproduce sexually.

Protista Classification

• Protists are classified based on how they obtain nutrition.
  • Autotrophs use chloroplasts to convert sunlight into food.
  • Heterotrophs ingest food particles from their environment for energy.
  • Mixotrophs ingest food particles and use sunlight for food.
• Protists are also classified by how they move.
  • Protists move using pseudopods, cilia, or flagella.

Protists Categorization

• Protists are classified into three main categories:
  • Plant-like protists
  • Animal-like protists
  • Fungus-like protists

Plant-like Protists

• Plant-like protists are commonly called algae.
• Algae are autotrophs that contain chlorophyll, a pigment that converts sunlight into glucose via photosynthesis.
• Algae live in oceans, ponds, or lakes, and are classified into 6 phyla.
• Examples of plant-like protists and their corresponding phyla:
  • Brown Algae (Phaeophyta)
  • Green Algae (Chlorophyta)
  • Red Algae (Rhodophyta)
  • Dinoflagellates (Pyrrophyta)
  • Euglenoids (Euglenophyta)
  • Diatoms (Chrysophyta)

Euglenophyta

• Euglenas can make their own food through photosynthesis, but during periods of darkness, they become heterotrophic and consume solid food.
• The two features allow them to become heterotrophic.

Plantlike: Diatoms

• Diatoms are often referred to as "algae in glass houses" because their walls are made of silica.
• Diatoms form the base of the aquatic food web.
• Diatoms are used in toothpaste, pest control, reflective paint, and to stabilize dynamite.

Plantlike: Dinoflagellates

• Dinoflagellates have two flagella.
• Dinoflagellates are mixotrophic.
• Most dinoflagellates are marine plankton.
• Algal blooms of dinoflagellates can cause toxic "red tides."

Plantlike: Green Algae

• Green algae are unicellular.
• Green algae are typically found in shallow waters.
• Green algae serve as primary producers in aquatic food chains.
• Green algae supply approximately 67% of the global oxygen.

Plantlike: Red and Brown Algae

• Red algae are multicellular and found in oceans.
• Brown algae are multicellular, store food as oil, and can form crude oil deposits over millions of years (e.g., kelp).
• Brown algae is the largest protist
• Excessive algae growth can lead to dead zones and eutrophication.

Animal-like Protists

• Animal-like protists are also called protozoa and are unicellular.
• Protozoa are heterotrophs that engulf their food (holozoic) or absorb predigested food (saprozic).
• Protozoa live in water or animal body fluid.
• Protozoa are classified by their locomotion:

Protozoa Classification

• Carcazoans (e.g., Amoeba); have pseudopods (false feet), are mostly free-living and feeds by phagocytosis and reproduce by binary fission.
• Flagellates (e.g., Trypanosoma); use whip-like flagella, are mostly parasitic living in tissues (Trypanosoma causes African sleeping sickness) and reproduce by longitudinal fission.
• Ciliates (e.g., paramecium); use cilia to beat like the oar of a boat, are free-moving and reproduce by binary fission and conjugation.
• Sporozoa (e.g., plasmodium); have no independent locomotion, are entirely parasitic, and have a spore-like stage.
• Amoeba can cause Amoebic Dysentery.
• Paramecium can cause Balantidiasis.
• Flagellates can cause Leishmania.
• Plasmodium can cause malaria.

Fungilike Protists

• Fungilike protists are also called slime molds.
• Slime molds prefer cool, shady, and moist places.
• Slime molds are heterotrophs, feeding on bacteria and decaying organic matter.
• Slime molds are saprophytic, digesting food externally and then absorbing it.
• They are not true fungi because they lack chitin in their walls.

Importance of Protists

• Protists can cause serious diseases like malaria and African sleeping sickness.
• Protists provide aquatic consumers with food.
• Protists supply 40% of the world's oxygen.
• Red/brown algae is used to make agar, ice cream, sushi, toothpaste, and makeup.
• Protists are involved in a variety of ecological relationships.
  • For example, coral rely on photosynthetic protists for food.

Characteristics of Plants

• Plants are multicellular.
• Plants are autotrophs, using photosynthesis to produce their own food (contain chlorophyll a and b).
• Plants are eukaryotes.
• Plants have cell walls made of cellulose.
• Plants are sessile.
• Plants are important in phosphorus, carbon, nitrogen, and water cycles.

Evolution of Plants

• Land plants evolved 500 million years ago.
• Plants is the evolutionary steps from most simple to more complex plants

Water to Land Adaptation

• Plants adapted to stand upright, prevent moisture loss via a waxy cuticle, control gas exchange via stomata, and conduct tissue for moving nutrients and wastes.
• Plants have rhizoids (pre-roots) and vascular tissue: xylem (transports water and dissolved materials) and phloem (transports sugar).
• Reproductive strategies for terrestrial environments include spores, cones, seeds, and flowers.

Bryophytes: Non-Vascular Plants

• Bryophytes lack vascular tissue.
  • Plants cannot deliver water to other parts of the plant, and rely on osmosis and diffusion to transport water and nutrients
• There are 3 phyla of bryophytes: mosses, liverworts and hornworts.
• Bryophytes plants are found in moist habitats.

Pteridophytes: Spore Producing Vascular Plants

• Pteridophytes formed first forests 350 million years ago.
• Pteridophytes have roots, rhizome (horizontal stem under the soil), leaves, and vascular tissue (allowed vertical growth).
• Examples include spore producing vascular plants
• Instead of a seed, these plants release spores
• When conditions are right, spores grow into new plants.
• Pteridophytes are found in moist habitats (so sperm can swim to an egg).

Seed-Producing Vascular Plants

• There are two types of seed-producing vascular plants: gymnosperms and angiosperms.
• They produce pollen instead of sperm swimming to the egg.
• Pollen is a waterproof and drought-resistant capsule that contains sperm.
• These properties allow pollen to be carried to the female tissues by wind or animals.
• The zygote is protected in a seed.
• Seeds can be dispersed (via water, wind, animals).
• Seeds remain dormant during harsh environments.

Gymnosperms

• Gymnosperms are "naked seeds."
• Seeds are exposed on the surface of cones.
• Sporophytes produce both male and female cones.
  • Male cones release pollen & female cones produce eggs.
  • When an egg is pollinated and fertilized within a female cone, an embryo develops within a seed.
• Gymnosperms have four phyla.
• Most gymnosperms have needle-like leaves with thick cuticles (both adaptations reduce water loss).
• Gymnosperms have large, shallow root systems that form a mycorrhizal relationship with symbiotic fungi.
• Many gymnosperms are well adapted to resist hot, dry summers and cold winters.

Angiosperms

• Angiosperms have stems, roots, leaves, vascular tissue, flowers, and fruit.
• Reproduction takes place within the flower.
• The male gametophyte is a pollen grain.
  • Some pollen is dispersed by wind, others attract animals to aid in dispersal.
• Fruit is a mature ovary with a seed.

Angiosperm Structure

• Common for flowering plants to have both male and female parts, or separate male and female flowers
• Anther: Site of meiosis to produce pollen grains that will make sperm
• Filament: Supports the anther
• Sepals: Outermost circle of floral parts
• Enclose the bud before it opens and protects the flower while it develops
• Stigma: Sticky to collect pollen
• Style: Supports the stigma
• Ovary: Site of meiosis to produce eggs
• Petals: Located just inside the sepals and are often brightly colored to attract pollinators

Angiosperm Characteristics

• Seeds vary in size and can stop growing or remain dormant if the environmental is unfavorable.
• Fruits are mature (ripened) ovaries.
• Angiosperms have two types of seeds.
  • Each seed contains either one ("mono") or two ("di") cotyledons.
  • A cotyledon is a structure that stores food used by the growing embryo during germination.
  • Monocots produce seeds in which the embryo has only 1 cotyledon (seed leaf).
  • Dicots produce seeds in which the embryo has two cotyledons.

Fungi

• Fungi were once classified in the Kingdom Plantae but have since been reclassified.
• Fungi are more closely related to animals than to plants.
• Fungi are eukaryotic
• Fungi are usually multicellular
• Fungi are heterotrophic
• Fungi are dependent on other organisms for nutrients
• Fungi’s cell walls contain chitin
  • Chitin is similar to the exoskeleton of insects and crustaceans
• Fungi are important for ecosystems as it helps to breakdown organic matter and recycle nutrients.

Structure of Multicellular Fungi

• Structure of fungi is designed to enhance their ability to absorb nutrients from their surroundings
• Hyphae threadlike tubes that secrete enzymes to environment where food is digestion
• Reproductive structure: produces tiny cells called spores
• Mycelium - collection of hyphae and absorb digested food
• Fungi release digestive enzymes to break down food externally, then absorb nutrients.
• 4 methods of nutrient uptake: parasitic, predatory, mutualistic and saprobic
• Feed on living organisms and absorb nutrients from host
• Some release toxic chemicals called neurotoxins and result in poisoning or death

Fungi Reproduction

• Some fungi reproduce asexually and some sexual, while others use both methods
• Asexual Reproduction: Budding, Fragmentation and Sporulation
• Budding - parent cell grows & a new daughter cell "buds" off (i.e. yeast use this method)
• Fragmentation - piece of mycelium break off and creates new
• Sporulation: fungi make spores which spread and grow into new fungi
• Sexual Reproduction: Sporangium Spores

Classification of Fungi

• Chytridimycota (chytrids)(zygote fungi)
• Zygomycota (sac fungi)
• Ascomycota (Club fungi)
• Basidiomycota (Imperfect fungi)
• Deuteromycot: ie. Parasitic fungi, penicillin and fungi that cause disease (athlete's foot, jock itch, yeast infections.)

Importance of Fungi

• Make Food: yeast, bread, mushrooms, cheese, soy sauce, tempeh and citric acid
• Make Antibiotics: Zone of dead bacteria
• Fungi can cause disease: athletes foot
• Can be great bio indicators: they do not grow in heavily polluted areas
• Decompose dead matter
• Recycle nutrients (nitrogen and carbon)
• Can be used for food (mushrooms can be eaten, yeast makes bread, wine and beer)
• Can be used to make antibiotics
• Mycorrhizae help plants survive in diverse environments
• Can cause disease in humans (i.e. yeast infections, athletes foot) and plants
• Lichens serve as great bio-indicators