🍄 Decomposers

Decomposers

• Recycle nutrients in ecosystem

• Primary important role

• STEPS: 1. Break down of wood and leaves, 2. Some nutrients are absorbed and used, 3. Rest is returned in soil and recycled

• Decomposition of dead org matter

Can archea be decomposers?

No!

Characteristics of bacteria (8)

• SOME are decomposers (not all of them)

• Unicellular and small

• LACK A NUCLEUS

• ONE CIRCULAR CHROMOSOME (simple genome)

• Most have a cell wall

• Ribosome structure diff from eukaryotic

• Reproduce asexually (division)

• Present everywhere

Anatomy of prokaryotes

• CELL WALL: outside of plasma membrane, very strong and resists bursting, maintains shape (provides structural support)

• CAPSULE: outside of cell wall, SOME prokaryotes only, prevents drying, STICKY AND ATTACHES EASILY, protection from white blood cells destruction

• Can be found in all types of metabolism (photoautotrophes, photohetero, etc.) and can be the only orgs in some of them

Oxygen and prokaryotes

• OBLIGATE AEROBES: requires O2 for cell. respiration

• FACULTATIVE ANAEROBES: will use O2 if present but can grow by fermentation in anaerobic environment (no O2)

• OBLIGATE ANAEROBE: poisoned by O2

Prokaryotes and quick adaptation

• Mutations are rare

• BUT reproduction is extremely fast

• THEREFORE mutations can increase genetic diversity through short periods of time and in large populations

Prokaryotic DNA and reproduction

• Not surrounded by membrane and located in cytoplasm

• Forms a chromosome in nucleoid region

• Genetic transmission in binary fission reproduction

Plasmids

• Circular DNA holding non-necessary genes —> “superpower”

• E.g.: metabolism, resistance virulence, etc.

• CONJUGATION: “sexual” transmission of plasmid between 2 diff individual, OF SAME GENERATION

• 1 bacterium can have many plasmids

• CAN be useful or useless: natural selection

Endospores

• Dormant, tough, non-reproductive structure produced by some species

• Ensures survival in extreme environment

Ecological significance of bacteria

• PATHOGENS (diseases)

• MUTUALISTIC SYMBIONTS: ex: herbivores unable to digest plan cellulose and bacteria doing it for them, our microbiote

• NITROGEN CYCLE: N2 in air must be converted to NH4+ and NO3- for plants (ammonium and nitrates)

What are fungi

• Eukaryotic

• Have CHITIN in cell walls

• Heterotrophs, absorb nutrients

• EXOENZYMES: secrete in outside environment, decomposer nutrients for absorption —> can breakdown polluants into non-toxic compounds (ex.: petroleum, PCB, pesticides or herbicides)

Anatomy of fungi and species diversity

• Hyphae: filaments composing mycelium

• Mycelium: all connective structure underground

• Bulb: simply reproductive structure

• Can be biggest organisms —> vary in size (Unicellular to complex multicellular)

• Yeast, mold, mushrooms

Lichens as mutualistic symbiosis

• Fungi + blue-green algae/cyanobacteria

• Alga provides fixed org carbon (food)

• Fungi provides algae minerals, water, shelter and SECRETED CHEMICALS which ward off predators/repel microbes

• lichens can break down rock into soil

• Lichens is food for caribous+ reindeer

• =/= moss

Mutualistic symbionts: Plants + fungi

• Mycorrhizae

• Important for healthy ecosystem

• Fungi mycorrihizae attached to roots of (almost) all vascular plants

• Fungus acquires organic carbon

• Fungus provides nutrients, water, pathogen resistance, increased resistance to toxic element in soil + enzymes solubilises nutrients + explore more volume of soil for the roots (Fungus is yellow hyphae)

Achlorophyllous plants

• Do not have chlorophyll —> cannot photosynth and produce CO2 to feed themselves

• Mycoheterotrophic: parasite mycorrhizae and steal the CO2 of linked photosynthetic plants