Eukaryotes Flashcards
protist
small eukaryotes
eukaryotes that are not plants, animals or fungi
most are unicellular (but not all)
very diverse
why was the kingdom Protista abandoned
genetic investigation revealed that many protists had more in common with plants, animals or fungi than with other protists
ongoing changes in understanding of phylogeny has changed the way we view the classification of eukaryotes. What are the 4 supergroups of eukaryotes
Excavata
SAR
Archaeplastida
Unikonta
Excavates
include protists with modified mitochondria (highly reduced) and protists with unique flagella
SAR
highly diverse - Stramenopila, Alveolata, Rhizaria
DNA similarities
diatoms amoebas dinoflagellates
Archaeplastida
red and green algae
plants
key photosynthetic species
red and green algae are the closest relatives of plants
unikonta
includes animals and fungi
amoeba
in endosymbiotic theory where do mitochondria come from
descended from bacterium engulfed by a host cell that was archaean
in endosymbiotic theory where did plastids come from
eukaryote engulfed cynobacteria (photosynthetic ) that then evolved into plastids ( a chloroplast is a type of plastid) (primary endosymbiosis)
this gave rise to red and green algae
(cyanobacteria are gram negative and have two cell membranes) - plastids in red and green algae also have two cell membranes
red and green algae engulfed by other eukaryotes (secondary endosymbiosis)
what is the closest relative to plants
green algae (protist) charophytes - have cuticles and stomata
types of plants
non vascular e.g. mosses - liverworts, mosses and hornworts
vascular - 93% of all plant species
Vascular divided into
-seedless - club mosses and ferns (lack seeds / spore forming)
- seed forming - gymnosperms (no casing for seed) and angiosperms (flowering plants seeds develop inside chambers)
what traits are shared by fungi
Nutrition -cannot make their own food
fungi do not ingest (no digestive system) - absorbs nutrients from outside their body
Body structure - multicellular filaments and single cells (yeasts)
nutrition in fungi
heterotrophs - cannot make their own food
absorb nutrients from their environment
secrete enzymes into their surroundings or use enzymes to penetrate cell walls of other organisms
can digest compounds from wide range of sources living or dead
fungi as decomposers
break down and absorb nutrients from non living organic material e.g. logs / corpses / wastes
parasitic fungi
absorb nutrients from the cells of living hosts
may be pathogenic
mutualistic fungi
absorb nutrients from a host but also give benefits e.g. fungi in digestive tracts
yeast
unicellular fungi - single cell
most fungi grow as filaments and relatively few species grow as single celled yeasts
hyphae
fungi are made of a network of tiny filaments called hyphae - mushrooms and underground mycelium are continuous networks of hyphae
hyphae consist of tubular cells walls surrounding the plasma membrane and cytoplasm of cells
what are hyphae made from
tubular cell walls that surround the nucleus and cytoplasm of cells
cell walls contain chitin (polysaccharide)
septa
in fungi hyphae are divided into cells by cross walls called septa (septum)
Septa have pores large enough to allow ribosomes, mitochondria and nuclei to flow from cell to cell
mycelium
fungal hyphae form an interwoven mass called mycelium
infiltrates the material on which fungi feeds
maximises surface to volume ratio
just 1 cubic centimetre of soil may contain 1 km of mycelium giving it 300 square cm of surface in contact with the soil
mycorrhizae
mutually beneficial relationships between plants and fungi
contain mycelial networks that penetrate the soil further than plant roots / more efficient nutrient acquisition
ectomycorrhizal fungi
grow over the plant root but do not penetrate
endomycorrhizal / arbuscular fungi
penetrate into the plant cell / extend arbuscules through the root cell
