Animal Plant Flashcards
mass extinction
=a mass extinction is a sharp spike in teh rate of extinction of species caused by a catastrophic event or rapid environmental change
scientists have been able to identify five mass extinctions in earths history each of which lead the loss of more than 75% of a species
a paradox
the smallest part about to destroy the others
traditional classification
Observation of nested character states
No subdivision betweeen ‘old’ and ‘derived’ New characters within taxonomy
Binomial classification – the species is the only stable taxonomic unit…
monophyletic group
= all sister groups + their unique common ancestor
synapomorphy =
= new character only shared between C and D sister groups and no other grouping
plesiomorphy =
= older
Character shared by several
taxa
Paraphyletic
Grouping
does not include all
Descendants of a common
Ancestor)
Emergence of cladistics
Numerical methods to establish relationships
are all humans bony fish? (osteichthhans)
-yes but we are also mammals and amniotes and tetrapods therefore as fish are not those three we do not share synamaporphies
remember the entire group is defined by
the synapomorphies of the last common ancestor of this monophyletic group.
Have the (i.e. all) dinosaurs died out at the end of the Cretaceous, after the meteorite impact 60Mya?
-no birds are decedents of dinos therefore some Dions survived
biomineralization =
is the process by which mineral crystals are deposited in the matrix of living organisms. This process gives rise to inorganic-based skeletal structures such as bone during development, which is a complex and dynamic organ with both structural and metabolic functions.
LOOK AT ORGIN OF EUKARYOTES
the TCA cycle already existed in archaebacteria
-biosyntehtic pathways
-lots of enzymes contain metals
origins of weathering the TCA
-These are
Acids release ions/metals
From rock into water:
Si, Fe, Cu, Ca, Mg,
Zinc
origins of weathering BY LOOKING AT TCA
Photosynthetic, TCA cycle dependent release of ions from granite, andesite..
Another key function of succinate, malate etc – ancient heritage archaea!
already happened 1.5 billion years ago!
Nummulites
single cell organisms with shells
chitin-silica scaffolds
on the inside the Golgi apparatus already evolved in
The common (eukaryotic) ancestor of radiolaria and all other metazoans
radiolarian fossils
The earliest found radiolarian fossils – about 500 million years old (Lower Cambrian), however, molecular data suggest an age of > 1billion years
Biomineralization is an ancient eukaryotic heritage
Which got lost again many times secondarily.
chitin at the heart of shaping the diatom shell
discovered enzymes that dissolves chitin
diatoms
Diatom cycle – sex..size ctrl.
Algal symbionts…
Make 1/5 of all oxygen that you breathe in every day!
Sensitive proxies for climate parameters.
Pattern of the Golgi defines pattern of the shells – cellulose and chitin as scaffolding.
Where does the silica come from?
Weathering of continents – photosynthesis! Why?
Acids…
Function of silica – uv light protection – buoyancy ctrl.
a bit of phylogenetic Thinking: how to determine
The evolutionary origin of a molecule…
Is PART OF OUR SHARED eukaryote ANCESTRY
Chitin was later LOST IN DEUTEROSTOMES – this is
why we don’t contain chitin…
although we like to eat it…
how often did multi-cellularity arise?
evolved Manu times independently many times therefore certain tools kit allows Multicellularity to occur
multicellularity principles
1.Aggregation – watch amazing slime mould movie here ! These are facultative metazoans/multicellular organisms
- Staying together after division :
Choanoflagellates.. - Facultative Multicellularity can solve many spatial problems to effectively harvest nutrients in a given area, see in this movie.
Or in this movie here! This tells you how over-rated the term ‘intelligence’ can actually be…..
phylogeny of metazoans
(currently accepted tree on the basis of millions of DNA sequence comparisons)Tree representsrelationships between groups!
The power of phylogenetics:
We can see a Stepwise assembly of the integrin cell adhesion system in our fungus-like Opisthokont ancestors
cilia were already there in our fungal opisthocont ancestors
another thing they have in common
phylogeny of metazoans
850-55 MYA
making glass is in our metazoan ancestry
ancestors of metazoans
Novelty: Choanoflagellates with microvili seams (actin filaments in red)
and silica skeleton ( white left).
whole genome sequencing of choanoflagellates (M.brevicolis)
provides unprecedented genomic insights into evolutionary novelties during the transition towards metazoans:
cadherins (later part of a unique cell adhesion/cell-cell recognition system)
were already there in common
Single cell opistokont ancestor of fungi- choano-
Flagellates and metazoans
New In Metazoans
h
to determine if we are in he 6th mass extinction can look
at cumulative extinctions
goes up in 1960s after oil begins to become cheap again (greenhouse gases)
we need technological solutions to this crisis for this you need to know
-how animals and plants work are built = this is written in the DNA in time and space
-and how they interact
metazoa
multiple cellular animals (us)
-833-560 MYA
photosynthetic activity created first mass catastrophe by archaebacteria because so much oxygen was in atmosphere
antioxidants evolved
excess oxygen useful for ATP therefore big drop in O once ETC evolved
(endosymbiosis)
Darwin proposed the theory of phylogenetic trees
that is why organisms look similar to each other (they are related)
outgroup
B shares fears with another species C but not with teh common ancestor of C and D (sister group)
cladistics
is a method of hypothesizing relationships among organisms — in other words, a method of reconstructing evolutionary trees. The basis of a cladistic analysis is data on the characters, or traits, of the organisms in which we are interested.
the entire group is determined by
the synapomorphies of the last common ancestor of this monophyletic group
osteichythyans
advent of premaxillary jaw contribution
we are oesteichthyans but we are also
tetrapods
tetrapods
means “four legs” in Greek. Amphibians, reptiles (including dinosaurs and birds) and mammals are the major groups of the Tetrapoda. Tetrapods include all land-living vertebrates, such as frogs, turtles, hawks, and lion
generating phylogenetic trees start with
D (last common ancestor)
the TCA cycle already existed in archaebacteria
these acids causing ions/metals to be released into the water from rock
-Si
-Fe
-Cu
-Ca
-Mg
-zinc
chitin-silican scaffolds on the inside of the golgi apparatus already evolved in the common
eukaryitic ancestor of radiolaria and ALL other mtazoans
earlier found radiolarian fossils about 500 million years old
however molecular data suggests an age of > 1 billion years
when chitin scaffold is dissolved sillica disolves too!
chitin at the heart if shaping diatom shell
where does the silica come from?
-weathering of continents - photosynthesis
-acids
function = UV light protection and buoyancy
pattern of the golgi defines patterns of the shells
cellulose and chitin as scaffolding
how often does multicellularity arise
evolved many times independently
hormones help control
outgroup of metazoans are the
choanofagelates
-apicobasal polarity inside single cells
opisthoconts
fungi + metazoa +chanoflagelates
the power of phylogenetics
we can see stepwise assembly of the integral cell adhesion system in our fungus-like opisthokont ancestors
one necessary functional complex is made of parts of which evolved at a different time
another thing opisthotonos have in common is cilia
were already in our fungal opisthocont ancestors
making glass is in our metazoan ancestry
novelty = choanoflaggelates with microvilli seams (actin filaments in red)
silica skeleton
microvilli at very base of evolvement of chanoflagellata and
metazoa
while genome sequencing of choanaflagellates
provides unprecedented genomic insights into evolutionary novelties during the transition towards metazoans
cadherins
later part of a unique cell adhesion/cell-cell recognition system
-were already there in common single cell opistokont ancestor of fungi- choanoflagellates and metazoans
new in metazoan
1)cadherins (see card earlier)
2)enormous gain of introns
3)exon shuffling as mechanism to generate novel genes
4)evolution of notch and hedgehog signalling molecules during the transistor from the common choanoflagelate ancestors to metazoans
trichoplax
two cell layers
no mesoderm
different cell types
trichoplaz sequenced
the first want ligand the first neuronal functionality within universalist cells signalling molecules to subdivide the organism adhesion molecules to keep cells together after division
first metazoans is the sponges
Porifera
they have choanocytes (have flagella)
first metazoans is the sponges
Porifera
they have choanocytes (have flagella)
significance of sponges
the solution to Darwins paradox why are there islands of biodiversity in otherwise nutritional deserts in the sea ? SPONGES
sponges feed the corals by providing particulate organic carbon.cellular detritus
therefore sponges at bottom of food chain
how all metazoan cells stick together
collagen genes evolved already very early and many got selectively lost in later lineages
first found in sponges the organ of epithelial sheets
collagens are required for basement membrane formation of all epithelial tissues in any metazoans body
how do we know sponges have stem cells?
ability to regenerate themselves
and give rise to multiple different cell types
flask cells in the sponge are the first ever doing EMT and they form the entire adult animal these cells
correspond to what us called the epiblast in vertebrates they are stem cells
-use notch pathway
cnidarian phylogenetic position
new evidence to assume that cnidarians are the sister group of all bilaterians
-evidence based on gastrulation(echo/endoderm)
diplobblasta
have three cell layers not two therefore definition is wrong
sponges cells/flask cells migrate into larval cell ball (EMT)but this does not lead to inner vs outer vs cells in between flask cells go on their own ->
cnidarians + all bilaterians :
new sheet invagination process to form endoderm vs ectoderm before EMT of
-stem cells that become mesoderm
-emergence of neuronal nets
-oral- aboral axis kept into adulthood
(NO ANUS YET)
invagination process
is the process of a surface folding in on itself to form a cavity, pouch or tube
gastrulation
-mesoderm formation (pre-bilaterian) by invagination of larval epithelium
-gastrulation to produce mesderm as third germ layer + an axis
-mesoderm gives rise to muscles, blood and gonads
-ectoderm gives rise to skin, neurons, CNS surface sensing of the environment
-endoderm gives rise to digestive epithelium and associated glands
cnidarian polyps have a head
same genes used in our head
larval specialisation 3 distinct nerve nets
-earliest gene for being a neuron is Soc b 2 gene
all metazoans are
sentient
3 cell types (neuronal systems
-nematocytes = explosive capsule to impact another organism (coral warfare)
how genes are
region specific across cnidarians and bilaterians
cnidarian ancestor of
bilaterians
an ancestor gene of nodal the key gene that
determines the vertebrate left-right body axis also determines asymmetric budding in cnidarians (and corals)
sponges transmit light when injured how?
luciferins are chlrophyll heme/flavin ring breakdown products
-the sclerocytes flash light upon regeneration this is transmitted via spicules to contractile pinacocytes/myocytes and sensed by the crypto chromes and effect endogenous oscillations (stem cells to source)
cytochrome’s as blue light sensors - and modulators of circadian rhythms
part of circadian rhythm
coral use cytochrome for reproducing
sensing moonlight
cnidarians sister group of
bilaterians
early larval stages show the transition to a bilaterian
as the anus is a bilaterian invention
cnidarian larvae and bilaterians look similar this raises questions but how are they similar
sensory systems at front end with brain
non bilateral vs bilaterian
non,
sensory systems at front end with some neurons
-body axis
-body appendages
-motile animal as larvae not adults
bilaterian
-keeps moving
-sensory systems at front end with brain
-body axis/worm like
-body appendages/legs
paedomorphosis
the adult stage of a descendent species looks like a larval/embroyonic stage of a phylogenetic ancestor
how to make a motile body axis from mesoderm
how genes on different chromosomes so bilaterians can use intron invasion to link them all together.(bilaterian novelty)
colinerrity of the hot cluster
how genes followed in order = colinaearity
full box cluster in bilaterian ancestor
-deutoerstome acestor
-protostome ancestor
-cnidarian ancestor of bilaterians
an ancestor gene of nodal
the key gene that determines the vertebrate left-right body axis also determines asymmetric budding in cnidarians
the left-right nodal (LEFTY PATHWAY) pathway emerges in bilaterians
old receptors get a new nodal ligand
nodal gene responsiblee for vertebrate L-R asymmetry
why are butterflies symmetrical (the lefty pathway)
the lefty pathway was lost in the ecdysozoa
when did the bilaterians evolve
520-580 MYA due to burrowing traces of animals
molecular says over 600 mya
parsimony
minimum number of transitions of characters within a given phylogenetic tree
evolution of body appendeges
all appendages depend on DII (distalleless) gene action BUT the instructions of how many legs an animal has evolved independently
the urbilaterian animal eyes
were already there but were LOCALISED to the front end in bilateral
old programmes get coopted to the front of the animals new brain
there was a pre-adaptation for big compound eyes (multiple pigment and cell pairs) which happened several times INDEPENDENTLY within bilateria
there are fundamental similarities of molecular and cellular organisation between arthropods and vertebrates suggest a sophisticated brain in
common bilaterian ancestor
for example both have pituitary glands
annelids
segmentation a head, a tail. How genes expressed in order in larval segments
in molluscs
teh hot clusters bread down again and become a motor of NOVELTY
ecdysozoa - group features
worm like (cycloneuralia)
appendages (pan arthropods)
ecdysozoa in context (abundance and diversity)
-today the most abundant animals are nematode worms or plankton-forming crustaceans
-most diverse are insects
encysozoa moulting evolved more than
500 MYA
onycophora (claw bearers)
-walking worms 14-43 Pairs of non-articulated legs
-papillae secrete adhesive material
-mouth with claws
-molts every 14 days
tardigrades exact position
still debating
-soke argue closer to nematodes than to arthropods
tardigrades simple body plan
-reproduce by parthenogenesis or male/female
-molts several times during its life
-lives up to year
-eats algae
tardigrades are extremophiles
-survive atmospheric conditions up to 20 years
-desiccated can live for decades at -80 °C
if enters DRY state then rehydrates
tardigrade intrinsically disorders proteins (TDPs) are enriched during dessication
slow drying ->desiccation -> rehydration
caenorhabdiditis elegant genetic model system
genome sequenced in 1988
-EVERY CELL DIVISION TRACKED
-apoptosis ->development (understood that certain cells die due to programmed cell death)
life cycle of a terrestrial, free living nematode
embroyo ->L1 -> L2 … L4 ->adult
life cycle of a nematode under stress
-enters Dauer (can resist starvation)after L2 which goes straight into L4
daters can migrate by hitchhiking arthropods
this will allow them to migrate to better conditions
parasitism
evolved several times independently
the Dauer of free-living species is very similar to infective stage of parasites
making people think parasitic nematodes evened from normal
Arthropods means
= jointed appendages
features of arthropods
-clear segmentation
-modified appendages
arthropods orginiated
-colonized land in the late Cambrian to early trilobites in fossil record - from Cambrian up to 251 MYA (permian)
ordovician (510 - 471 MYA)
arthropods exoskeleton (good for when they were water bound)
-protein
-chitin
-new locomotor/gas exchange solutions can’t move like a worm
-arthropod (jointed foot)
-influence on land invasion
crustacea
mostly marine
mutations in how protein correlate with body plan evolution
-6 legged insects diverged from crustacean-like ancestor with multiple limbs
one group of chelicerates mites
-some are parasites
-Gravid pyemotes Barbara (eggs grow inside mother and the males/females mate)
-males/females eat mother from inside out
symbioisis of coral and photosynthetic algae
algae obviously provide photosynthesis products (most importantly photosystem 2 which splits water)
coral provide CARBON
what do teh corals do for the dianoflagellate
protection with the green fluorescent protein.
because different pigments can absorb different lights
the sleeping dog of immunity is awakened in corals bleaching
symbiont algae shut down the endogenous apoptosis inducing machinery
-with global warming this system breaks down and the symbiont is thrown out and coral dies (without nutrients)
attack of photosystems
no protection from host any longer - bleaching
process of calcification
hydrogen moving out of space so calcium moves in via transporter.
-proton H=/Ca ATPase pumps are the key targets and victims of acidified oceans
essentials of carbon fixation and biomineralization
carbonate and calcium must combine for biomineralisation
coral has 2 carbonic anhydrase enzymes (one makes rock and the thermoses hydrogen out of space
reduction in sea water pH result in significant reduction in pH of
calcifying fluid
take reactant out equilibrium shifts
to the reactant side so more bicarbonate
temperature as driver of pH changes where it matters - carbonic anhydrase are the targets of our destruction
-the higher the sea water temp the lower the pH and the less CO3 available for biomineralization
carbonic anhydrases are particularly sensitive to small reuctions in pH
the lower the pH
the lower the calcification rate
directly proportional
he higher the temp
the lower the calcification rate
INdirectly proportional
algae can create buffer
system at breaking points which is therefore beneficial for the algae (carbonic anhydrase)
lophotrochozoa
comprises annelids and molluscs
close to bilaterians
molluscs- common ancestor
-head with radula
-foot and intestinal sac
-mantle - biomineralizes into
-shell in some (snails bivalves = mussels, air chambers in CONCHIFERAN DESCENDENTS)
-uses chitin for shell bxomineral nucleation (calcium carbonate)
ancient segmentation of some molluscs - probably from common bilaterian ancestor gets lost in the crown molluscs
-a basic mollusc - polyplacophoran. it is unclear if their segmented nature is a primitive feature of all molluscs and shared feature with annelids (or even bilaterians)
Eric kandel discovered the molecular mechanisms of long term memory storage using the mollusc aplasia
found cAMP and Kreb involved in memory formation
gains and losses of shells
-shells evolved in conchifera and got lost several tikes independently again
deuterostomes contain
chordates(craniates amphioxus and tunicates all have notochord)
echinoderms all have
hemichordates
hox gene order - collinearity of gene order and expression maintained- just one cluster like in ascidians and amphioxus
teh notochord is an essential signalling centre
however some of these features evolved already in a common deuterostome ancestor
cooption of signalling centre by notochord
sonic hedgehog molecule
patterns the developing embryo using a concentration gradient
teh notochord and neural tube - key inventions of all chordates
germ layers- ectoderm blue
endoderm - yellow
mesoderm - red/green
left right asymmetry of mesoderm is because
nodal pathway is active
turichates - Ciona (ascidian) teh simplest chordate
can track each cell division
teh turnichte larva but not adult look like chordates
all other chordates (us included)
can be thought of as larval ‘retards’
developmental arrest as an evolutionary strategy (pedomorphosis)
has brain cells and pituitary gland
truncates in their notocord
cellulose synthesis Inecessary for metamorphosis
notochord = chordates
a vast cross-species comparison gives the answer
striking similarity of truncate cellulose synthase to related gene of a cyanobacteria symbiont (notsoc)
horizontal gene transfer unique to
tunicate lineage
the early chordate/tunicate brain
certain markers to become eyes (retina cells)
potential for hindbrain
reutilisation of Pax6
programme within the brain
neural crest cells as
4th germ layer
-Hox genes inside neural crest
-NC forming skeleton
somatic vertebrae
neural crest sheaths
three sheaths form at base of vertebrates
crenate and amphioxus chordate shared filter feeding
gill basket BUT cartilage/skeleton
(derived from neural crest cells)
vertebrates craniates
neural crest
tissue generating and organising a branchial apparatus
yellow CNS-brain
green notochord
blue cartilage
the head of jawed vertebrates
chondrocranium - originally made of cartilage, later either replaced by endochondral ossification
or covered by bone (through dermal ossification)
viserocraniu or spanchnocranium - cartagnious and dermal bone parts surrounding
palatoquadrate (important)
upper jaw of the vertebrates
first ever predator
had compound eyes
giant arthropods predators roaming the Cambrian seas
anomalocaris
hard tissues
the arthropods were well ahead of the vertebrates by (at least 50-100 MYA)
our chordate/vertebrae ancestors were arthropod food for a long term
Palaeontology informs us about the deep evolution of structures:
why oeistchythyans are not the first fish with bones
-placoderms first with jaws
-Bony fish evolved fro the common ancestor Osteostracans, placoderms and shark
hesterostracans
dark area had electrical currents
enamel outer layer
evolution of vertebrate skeleton in steps
-cartillage no bone ancestor
-dermal bone, acellular (no cells inside) enamel caps
-cellular dermal bone pectoral fins
-extensive bone remodelling, teeth
shark have secondary
dermal bone loss
two Different types of bone formation
1)dermal
-bone sheet formation directly from mesenchyme the oldest ossification form - in the gnathostome stem : astraspis hesterostracans
2)endochondral ossification
-cartilage formation first - to be replaced by bone
-the last form of ossification evolving - in placoderms the first gnathostomes with proper jaws
hesterostracan fish and juvenile placoderm have
remarkably similar dermal bone ontogeny
key embryological components of all crown gnathostomes
-hindbrain
-brnchial arches
-mesodermal limb buds
-mesodermal somites
neural crest segmentation retained in muscle attachment system
matching between hindbrain
-segment
-neural crest in branchial arch
-and its innervation by hindbrain
giant sea scorpions arms race lead to
giant placoderms (first vertebrate with proper jaws)
they have tooth like denticles all over their body to generate laminar flow along it
structure of shark teeth (similar to humans)
they can regenerate teeth through life (revolver dentition)
key embryological components of all crown gnathostomes
-hindbrains
-branchial arches
-mesodermal limb buds
-mesodermal somites
osteichthyan chondrocranium =
cartilage the endochondral ossification
osteichthyan dermatocranium =
dermal ossification
osteichthyan lower jaw
mockers cartalige
osteichthyan part of jaw that joins
quadrate
osteichthyan top jaw
palatoquadrate
osteichthyan back part of jaw
hyomandibula
entelognathus - placoderm
very close to osteichthyan stem group
two nostrils on each side
teh crown gnathostome micrometry gets inherited to
osteichthhans micrometry is secondary loss
origins of lungs
actinopterygll all had the basis of lungs
ventral lungs evolved before
when did the osteichythyan liveq
silirian time period
high CO2 levels for a very long period of time
earliest arthropod trackway fossils on land:
488 MYA (shortly after Cambrian/ordovician transition)
arthropods related to myriapods
early radiation of tetrapods happens in a time of low oxygen/high CO2
new methods of breathing (lung vs gill)
probably with lung being additional air storage device in low oxygenated waters - greenhouse effect
tetrapods move onto land AFTER
end devonian <362 MYA
evolutionary novelties within the tetrapodomorphs
evolution in steps
- a primary palate direct opening of nasal cavity into mouth = china
-another sarcoterygian novelty: a toungue
eusthenopteron:
principles of a sarcotergian fish head
endochondral
capsules around nose and inner ear (no hearing)
the choana
-two nostrils in a fish (osteithycan even in placoderms = a crown gnathstme feature
-in tetrapods there is only 1 nostril outside the china is the second posterior nostril in fish
evolution of teh choanae
1)inwards motion of the posterior nostril
2)freeing the neck dissolution of the head-shoulder junction in the dermal armour
loss of dermal cheek bones in transistor from fish
3)hearing - hyomandibula = stapes + tympanic membrane hearing (acanthostega one of the first few tetrapods)
evolution of choanae cotinued
-fish hyomandbula bone turns into tetrapods stapes single hearing bone of all tetrapods establishing new connection in inner ear fenestra ovalis
assembly of the hand 8 fingers
-compariosn between extra tetrapods would suggest that the ancestors all had 5 fingers(digits) there were digits before animals went on land and we have footprints
key early steps of tetrapod limb and girdle evolution
gradual loss of dermal body armour in head and neck region
how can one reconstruct ancient climates
count the number of stomata in fossil plants
it is the biosphere that drove down atmospheric CO2 levels into the ground
oceanic algae - photosynthesis - deposition
biominerilization
forest ecosystems
Amniote phylogeny climate
firm transition onto land happened within the amniotes but not in teh early amniotes : eggs on land with egg shells and amnions protecting embryos against drying out
tetrapod tree
tetrapodmorphs (tetrapod stem group)
some are aquatic still;; and some are terrestrial
aquatic vs terrestrial lifestyle does not map to tetrapods
it emerged (and got lost) repeatedly in the tetrapod crown groups
mixed early amniote lifestyles
amphibious/terrestrial/aquatic
early amniotes had juveniles with gills - like tadpoles
tetrapods are terrestrial or
amphibious
large subdivisions of amniotes
one group is reptiles and teh other is thesnapsids
amniotes developed scaly skin because
change of dominant climate
where did the first amniotes emerge
in carboniferous forests around equator (warm and wet)
early tetrapods were living in high CO2 atmosphere so very different periods
amniote hearing system
all can hear
hair cells are overlaying little particles called oltoconia
pectoral membrane vibrates allowing hearing to occur
within cochlear (tonotopic) different hairs different frequencies
mechanosensory cells themselves go back to common ancestry of choanaflagellates and metazoans
so major evolutionary transformation happened in the 3D configuration of these mechanosensory cells
hearing system has three cannals
the semicircular canals they can feel flow of water coming in sharks
every motion of head moves liquid in inner ear (inertia)
look at where they evolved one semicircular canal
in the gnathostomes there are three semicircular canals
fish hyomandibula bone turns into tetrapod stapes
single hearing bone of all tetrapods establishing new connection to the inner ear
when people looked at early amniote
teeth inserted into jaw making it more stable
VERY SMALL
otic notch for tympanic membrane (eardrum) had evolved in tetrapods
stem amniotes had lost hearing again! no eardrum or otic notch
parareptiles have optic notch
again
3 times independent evolution of inner ear hair cells and re-evikution of tympanic middle ears in ammnioes
synapsids, archosaurs and lepidosaurs
basal papila becomes
cochlear
new forms of teeth amniotes
every osteo and placoderm has teeth so no novelty but thecodonty
thecodonty
teeth get embedded into/surrounded by alveolar bone: replacement teeth true heterodonty (different types of teeth in mouth) molariform vs incisiform teeth
vertebrae evolution across amniotes
number of vertebrae stays same in mammals but not amniotes and this comes about by how genes
shifts in sizes of hot genes expression domains changes number of vertebrae a given type
therefore diversity
novelties of metabolism in amniotes
stepwise miniaturisation of RBC in teh amniotes enabled higher degree of oxygen transport and metabolism = homeothermy
further miniaturisation by nuclear loss : probably cynodont synapsids
amniotes have complex lungs
various chamber systems
base of ammonites have scales
amphibian skin has almost no keratin and breathe through skin but reptiles have have thick layer of keratin and pigment cells that allow chameleons to change its colours
archosaurs
large sinuses (yellow blue)
fill the skull of archosaurs
allows light weight structures
all archosaurs have pneumatized bones permit low-weight large sizes part of bigger air sac systems
endothermy in amniotes
more elaborate in theropod dinosaurs ; birds
enabled nocturnal lifestyle
social lifestyle in burrows of diapsid amniotes
able to deal with high CO2 levels in enclosed spaces
modifications of pentadactyl
some fingers become invisible and disappear can turn entire fingers into wings
hair teeth and feathers develop the same
placed develops into bud then morphogenesis and adult organ
differences between amniotes and synapsids
Skull Structure: Another key difference is seen in their skull structure. Synapsids have a single temporal opening (temporal fenestra) behind the eye socket on each side of the skull. In contrast, amniotes have two temporal openings, known as diapsids. This difference in skull structure is crucial for understanding the evolutionary relationships between various groups of reptiles and mammals.
DIFFERNCE in lower jaw as one has hinge
sauria, diapsids diversification in
permian happened deep in early carbonifierous
permian period
fossil became as big as elephants towards end
key taxonomic groups of synapsids
cynodonts
therapsids = features evolved over time formation of hard palate
palates evolved many times independently and
got lost again within the synapsids
thinaxidon
key middle ear changes
amniote glands are the organs of
breasts
the Wilkes crater impact and the great dying 252.3 MYA
likely caused teh magma flows of teh Siberian trap system leading to the permotriassic catastrophe
bigger impact than the one that wiped out the dinos
siberian trap
volcanic system eruption
the great dying at the perm-triassic boundary
-massive volcanic activity extinguished within a maximum of 60,000 yrs more than 75% of all tetrapods
-90% of all marine reptiles
-it is assumed that sever hypercapnia is the key cause for this mass extinction
resilience of synapsid ancestor against hypercapnia
may be teh basis of a fossorial lifestyle and eusociality (which creates lots of hypercapnia and hypoxia in small protective burrows) these historical conditions are resented in COPD patients
loss of tympanic hearing in stem ammniotes brain fact of stapes
regain of hearing
gauss reichert theory
which has proven entirely correct on fossil record 3 ossicles of the mammalian middle ear callus incus and stapes respond quite accurately to the jaw
synapsid tree sows with teh ear
that the ear drum sits on lower jaw and moves lower to jaw to create vibrations
the new synapsid ear drum will develop in the lower jaw
-lower jaw structure the same osteichythan configuration denture still the only tooth breaking bone and flat
evolution of the dentary bone
elevation of bone at back
middle ear cavity hollowing out all outside of lower jaw
denture bone shape changes within cynodonts
evolution of jaw joint
primary jaw joint ends up in middle ear
trigemina ganglion
outside the ancient skull wall in amniote ancestrs
trigemina ganglion inside teh cynodonts/mammales
ancient palotoquadrate - neural crest fuses to skull and makes new wall on the outside of trigerminal ganglion
mammalian evolution massive plant diversifications
synchronous to/followed by
1)flying insect (pterygotes evolution - silurian/devonian)
2)wing folding
in carbiniforus
1)flying insect
2\0wing folding AND CATERPILLARS/LARVAE IN CARBINIFEROUS
order of evolution to mammals
-tetrapods
-amniotes
-synapsids
-archosaur radiation
-small mammals
carboniferous + permian
oxygen rich permitting high metabolism rates
after the great fire phanerozoic
only burrowing animals survived
changes in RBC
making them smaller and enucleating them
species richness before and after PT catastrophe
after crisis small synapsids disappear therefore more resources for them
reptiles start growing after
the nocturnal bottleneck in triassic/jurassic - losses and gains
massive insect diversification
become not nocturnal
nocturnal dominance in ancestors of
mammalian and marsupial groups
the nocturnal bottleneck in the triassic
loss of gadusol genes for UV sun protection
in the ancestry of mammals
what isn’t used gets lost
massive loss of opsin genes (visual losses)
the longer the gestation time
usually the bigger the animal the less it sleeps and the less energy it loses
volume of the liver determines
the amount of heat produced
surface of the skin
determines the loss of heat
surface of lung
determines O2/CO2 exchange capacity : the metabolic rate in smaller animals
synapsids and mmaliaforms retain nocturnal lifestyle
from amniotes
plesiomorphy
he ancestral character state for a particular clade. This character state may change depending on the clade under consideration. For example, “has four legs” is plesiomorphic for the clade of terrestrial vertebrates, but “has two legs and two wings” is plesiomorphic for the clade of owls.
synapsids and ammalianforms train nocturnal lifestyle which is detected by
the ear drum (tympanic) evolved at least 2 times independently within the ammniotes
new inner ear of mammal evolution
hair cell types evolve in that nocturnal period a well
the primary jaw joint ends up
in teh middle ear
in probainognathus we have two joints acting simultaneously
enormous variety of mimicry amount butterflies/moths copying snakes
geeks birds etc …
mammals significant increase in
encephalisation/cortical growth
change in sensory modalities in therians
increase in auditory and somatosensory
cortex sizes in the nocturnal placental ancestors this trend gets lost again later
cretaceous
living mammals in two major groups
-prototherians = duck billed lack a placenta lay eggs
-therians all other animals
small mammals coexisted with dinosaurs for millions of years mammals increased in size and number after the extinction of dinos
virus protein capture enables placentalia
they invade layer then make placenta
dawn of the hominis
Found in the sahel area (Sahara), shows that the earliest hominids were wide ranging across Africa – the impression one gets from the fossil record is that the story of hominin evolution is restricted to Eastern and Southern Africa.
the hominid
Hominids = Great apes + gibbons
Hominins = after the split with Pan
Note positions of the Miocene apes – Dryopithecus, Sivapithecus
Ardipithecus ramidus
5.8-4.4 Mya – shown as bipedal, would have stood 1.2M high.
The Taung child
-was roundly rejected at the time as an ancestor of humans, because of low brain capacity
-could be the cradle of mankind (the first ‘missing link’ was java man found in 1894 by Dubois, which was later, and had a larger brain – more acceptable!!)
The laetoli footprints
3.6 Mya – defnitive evidence of bipedalism, made by 3 hominins, 3rd stepping inside the prints of the 2nd.
Lucy
Highly sexually dimorphic species. Hadar. Small brain – around 400cm3.
Lucy was a climber and a walker
-discovered in Ethiopia
-Pelvis is Lucy has turned round to form a shallow support of the viscera of the body. Legs are still quite lateral – a bit of a waddle going on. Human pelvis is deeper, more bowl shaped, legs more anteriorly held
-Lucy would have been able to give birth to a baby with brain weight limited to 140-160g.
less developed at birth linked to changes in life history
Less developed infants means more care required, longer development phase. We see a trend towards longevity and loss of fertility in adult life. Adaptation to improved care by grandparents – a social evolution. Life history can be inferred by dental development differences between humans and chimps – we see a shift towards a more human order.
Upright gait is far more energy efficient….for standing upright
-Why stand up? Bipedalism and quadrapedalism are energetically similar. Unlikely to be an energy advantage initially.
-bipedalism is actually ancestral, knuckle walking in chimps a derived trait. Increased ranging on the ground may then have selected for the associated anatomical changes. Certainly savannahs were expanding at this time.
features of robust morphology
Australopithecine trend towards heavier grinding with stronger muscle attachments, and a flattening and deepening of the face.
Hominins evolved during a changing climate
Robustus seems to have been better adapted to the savannah environment, the more gracile forms were better adapted to semi-wooded environments. Robustus persisted, while the genus Homo evolved from either the africanus or afarensis lineages.
many hominid?
debate still about whether various lineages should be grouped together, and just represent a wide range of phenotypes. A common theme throughout all the anthropological evidence. Often groups do not neatly separate, but contain individuals with the odd trait associated with another. Reminiscent of gene frequencies in different populations.
Broad trend to increasing brain capacity
Encephalization quotients – increased brain size for a given body weight over time.
Cultural evolution: stone traditions
Oldowan started with Australopithecines 2.5 Mya, and persisted for a million years. The Acheulian industry, more complex, is associated with Homo erectus (but later erectus), beginning about 1.7 Mya.
Homo habilis: home maker…..one or two species?
Many think that the morphological distance between Australopithecus and Homo erectus is too narrow to accommodate another species. Some argue that the dimorphism observed may actually be two species, H. rudolfensis being the other. Unresolved.
Note that some argue that Homo sapiens comes directly from H. habilis, and H erectus is a side branch entirely.
Why the enlarging brain trend?
-male hunting
-expensive tissue hypothesis
-scavenging
-plant use
-no one really knows probably many factors involved
Java man the first missing link
Ernst Haeckel coined the term Pithecanthropus (ape man) from Darwin’s prediction of a missing link. Eugene Dubois found this missing link in Java in 1894, and termed it Pithecanthropus. Now considered H. erectus, but he rejected that resolutely, and insisted it was a gibbon (he thought gibbons were the missing link).
H. erectus expansion into SE Asia
Dtaes now suggest that H. erectus reached Java as much as 1.7 Mya years ago, meaning a very early dispersal out of Africa.
The enigma of Flores
Flores has H. erectus by 800 Kya, which would have required seafaring, which is incredible in itself. The ‘hobbit’ later on only has a brain volume of 417cc – same as early Australopithecines, human neonate of a chimpanzee! Doesn’t add up yet – they should not be cognitively capable of seafaring.
More SE Asian hominins
Homo luzonensis, 67,000 years, oldest Homo in Phillipines. Tooth morphometrics place it as distinct from archaic humans, modern humans, erectus and floresiensis, although finger bones (below) suggest resemblance to Australopithecus.
divergence of African and asian H erectus
Oldest African H. erectus dates from 1.89-1.95 Mya from Koobi Fora in E Africa – older than Asian.
Mixture of traits – curious thing is H. erectus in regions show traits that exist to this day in modern populations, such as high cheek bones in East Asian populations. Suggests some kind of continuity, but would also require parallel evolution around the world.
Asian H. erectus lacked Acheulian industry
Acheulian industry begins 1.5Mya with H. erectus in Africa, Asian H. erectus does not have this, which suggests it left before, which fits with the Java dates. Which means they left Africa early, which may explain some of the primitive traits such as sagittal keel.
Turkana boy
The most complete H. erectus skeleton (1.65Mya). Would have stood at 6 foot if had lived to maturity. Has modern body proportions. There is a trend in H. erectus for elongation of legs, and tall slim frame.
locomotor evolution
Tall slim proportions there by 1.8 Mya in Homo erectus – long legs good for running. Surface area to volume ratio (shown in brackets) allows the loss of heat, sweating very efficient. Adapted to running long distances. H. erectus spread like a weed through the world in a generalist niche.
Archaic humans
Hard to define group that sit between H. erectus and Homo sapiens and Homo neanderthalis. Start appearing just over a million years ago
Oldest modern Homo sapiens
315 KYRS OLD SHOWS THAT HOMO evolution was across the entire continent
Oldest Homo sapiens
Morphometric analysis shows it to be like recent modern humans (RMH), but still in evolving. A. facial shape – already there B. endocranial shape, between archaic humans and erectus
Modern Homo sapiens leaves Africa
177-194 Kyr ago, Misliya Cave, Levant. Tooth morphology shows sample to be modern human: grey modern humans; black Neanderthal; green early modern humans; violet Archaic humans (European)
the invasion of the land by plants was really the invasion of the air
-dessication and support are the principal problems
-adapting to desiccation requires a cuticle, spores and seeds and vascular tissue
Land plant =
=any photosynthetic eukaryote that can survive and sexually reproduce on land
all land plants are
embryo-bytes = embryo bearing plants
Embryophytes
have a true alternation of generations with MULTICELLULAR diploid and HAPLOID phases
embryophyte lifecycle involves
1)dipole stage (sporophyte) which produces spores by MEIOSIS therefore haploid
2)spores leave the sporophyte and grow into different kind of plant known as gametophyte so plants have 2 sets of organisms which look nothing alike
3)Gameotophyte produce gametes by MITOSIS
paraphyletic =
having multiple origins
plants evolved from algae but algae are not
plants
Alga is a term for multicellular organisms from a single cell
-leap to multicellularity occurred several times
-Algae emerged from primordial slime
the most likely ancestor to embryophytess was in the charales
-shared dervivd characteristics
-photosynthetic pigments
-starch as food reserve
-flagella type on motile cells
-coelochates retain fertilised egg
Charaphytes are algae most similar to
plants
Embryophytes have an archegonium and multicellular sporophyte WHAT DOES THIS MEAN
Spores = adaptation to dry conditions
multicellular sporophyte = adaptation to air dispersal
A choice of two directions for plants
become polikilohydric or amplification of sporophyte
A choice of two directions for plants
better adapted for moist evironments than tracheophytes
Polikilohydric =
Moist environments
1)amplification of gameotophyte produce gametes and ensure fertilisation and maintain sporophyte
2)non-vascular
3)bryophytes (mosses liverwarts and hornworts)
why do gametophytes need to be moisture hugging
they are motile games therefore are adapted to damp places
A choice of two directions for plants
better adapted for dry environments than bryophytes
amplification of sporophyte =
dry environments
-vascular
-tracheophytes (ferns lycopods horsetails and seed plants)
sporophyte
-disseminate meiospores in a terrestrial landscape wind is readily available and It favours height for dispersal therefore require vascularitissue (FICKS LAW OF DIFFUSION)
Evidence of land plants 480-360 MYA
-in ordovician
-fossil spores with sporapollenin and cuticle sheets occur in 458 MYA in Libya
-cuticles and stomata = land adaptation disadvantage in water
-archegonium and sporopollenin walled spores
-vascular systems
spores with trite markings are evidence of meiosis requiring a diploid progenitor
-COOKSONIA and RHYNIA show the sporophyte part of the sporophyte part of the plant
earliest land fossil
-fungus 440 MYA
Bryophytes are not monophyletic
-mosses have shared derived features with tracheophytes (by DNA and morphological features) actually have primitive vascular system
Heterospory
In the Devonian vascular plants had sporophytes that freely shed spores in the air
-unisexual gameotphytes manfest as heterosporous
plants that release spores =
pteridophytes
Heterospory once gametophytes are seperated
into male and female makes sense to invest more energy into female egg hence these spores become larger
why do heterospory which seems energy expensive
-increase energy in female gametophyte because maximum chances of successful fertilisation by making male spore more numerous
heterospory is said to increase convergence
11 times (BATEMAN and Dimichele 1994)
the logical progression of heterospory
increasing investment in megaspore causes reduction in megaspore number
-the difference in resource allocation between micro/megaspores follows a logical series which is invisible in fossils
-first there are sporangia become specialised producing only one or other of the spore types
once sporangia become specialised ->
megaspore energy investment may increase
seed habit - the next step after heterospory
-retain megaspore in megasporangium
-redude functional megaspores to 1
-retain megagametophyte
-modification of megasporangia to receive microspores
-modification of microspores to enable them to deliver sperm cells to eggs
-integument develops around megasporangia
spermatophytes =
all seed plants
gymnosperms =
first seed plants
megagameotophyte became a parasitic organisms living in
sporophyte
oldest progenitor to seed plants 385 MYA (mid Devonian)
the protogynosperm not technically seeds yet
growing tall tracheids and lignophytes
-first modern tree up to 30m in height evolved in Devonian although oldest calixylon fossils are givetian
archaeopteris had lateral buds which
allowed growth
bifacial cambium
lead to development of deeper root system
Finds of archaeopteridales
-britain in centre where archaeopteridales have been found they became distributed worldwide
movement up the plant: physics of growing tall
-root pressure = sugars and minerals secreted into xylem by root cells and Draw in water via osmosis
transpiration = tension-cohesion theory air danger
lycopods developed into trees after the
carboniferous which restricted amounts of wood
archaeopteris success included the development of a bifacial cambium allowing intermediate growth
convergence on tree habit
-made up of clubmoss trees
-plants have invented trees at least half a dozen times there are gymnosperm and angiosperm
the late arrival of leaves with archeopteris in late devonian
-leaves were nt needed before the atmosphere was CO2 rich through most of the Devonian
leaf evolution associated with falling
CO2 levels
by the carboniferous plants had evolved most of their features
the trees were clubhouses and horsetails
200 million years of non major innovations then angiosperm
appear
pollen is evidence
evolution of angiosperms
-innovation of the flower led to an explosion in species numbers
flowers = isolating mechanisms (reproductive isolation)
Rapid genome sizing in angiosperms
-during cretaceous ability to outcompete is suggested to be due to many hypotheses
-angiosperms developed leaves with smaller more numerous stomata
oldest flower fossils circa
125 MYA
parallel evolution of C4 in a cooling climate
-C4 physiology mechanism to increase CO2 concentration around Rubisco done by having CO2 fixed into 4C molecule therefore enabling CO2 to be delivered to chloroplasts
Evolutionary trends convergence on cactus habit
-some are cacti and some are euphorbia
cacti thorns = modified leaves
euphorbia = modified branches
evolutionary trends genome obesity
-many instances of polyploidy because they are simpler they can survive a doubled genome (happens under stress)
-polploids become diploids over time
Floral evolution - protection to attraction Angiosperms have
smaller cells which means they have an increased density of leaf structure
-male and female parts evolve
Fusion of carpels (syncarpy)
allows multiple fertilisation from a single pollination
Petals thought to have arrived from teh sterile forms of flattened stamens which served as pollen sources but also protection
as pollen sources but also protection
Differences between dicotyledons and monocotyledons
-differences in the numbers of petals
monocots tend to have less complex leaf structures
dicots are at the base of the
angiosperms
monocots are
the monophyletic group
base of dicots there are still
not true petal formations
basic anatomy of flower is described in
whorls
whorls sit on
recepticale
Honma and Goto 2001
-Whorls are dictated by MADS genes
-PI and AP3 upregulated produces petals instead of leaves,
upregulation of Ag as well makes everything a stamen.
MADs genes are the HOX genes of
plants
Angiosperm evolution is tied to teh evolution of MADS genes
-minichromosome maintenance ,1, Agamous(Ag), Defciens (Def), Serum response factor(SRF)
-evolved from topoisomerase
-few genes in animals , 20 in mosses >100 in angiosperms
-transcription factors- bind to CArG boxes
MADs genes are basically
transcription factors
they have proliferated a lot
Amino acid sequence large letters mean that
all amino acids have that letter
motifs become very visible
two types of MADs genes
TypE 1
-Malpha, M beta and M gamma
-1 - 2 exons
faster birth and death rate
more small scale duplications
Two types of MADS genes
type 2
sub types = MIKC^c, MIKC*
-7 exons
-lower birth/death rate
more ofte retained after genome duplications
heterostyly
the condition (e.g. in primroses) of having styles of different lengths relative to the stamens in the flowers of different individual plants, to reduce self-fertilization.
heteroanthy
In this length of filaments and styles in a flower are different. If the styles are of different lengths it is called heterostyly while if the stamens are of different lengths it is called heteroanthy.
three ways to classify fruits
-developmental organ of the fruit body in relation to inflorescence structure and pistil number
-true or accessory are they dervied from the ovary wall or other tissue
-morphological types
Austrolopithecus
Australopithecus is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera Homo, Paranthropus, and Kenyanthropus evolved from some Australopithecus species.
Plant domestication syndrome
increase grain size
loss of seed dispersal
loss of photoperiod sensitivity
architectural changes
synchronicity of development
cooksonia and hostinella
must be one common ancestor
the red list
aims to pinpoint endangered species
only 3% of known species have been assessed
ow many species on red list
16000
cause of background extinction
-result of biotic interactions (ecological and evolutionary, gradually changing climates landscapes and in teh case of small populations CHANCE
inbreeding depression
-mutation load
-less fit
-downward spiral
genetic consequences of falling populations
-small fragmented isolated populations
-reduced N
-reduced adaptabilitty
extinction within a region
-following a perturbation ,rate at which species form increases, then levels off or even decreases as all of the ecolgical niches become filled
-at the same time, extinction rates continue to rise as species are forced into ever more narrow waysof life
-system reaches equlibrium
species restricted to marginal habitats
-habitat has deteriorated
-can die of stravation or predation
-results in inbreeding
genetic drift in small populations can lead to
extinction
magnitude of background extinction
-99% of all species that have ever existed on earth are now gone
-based on fossil record most species exist for 4-22 million years
background extinction
-typically continuous species in a relatively short period of geological time can also be caused by environemntal or biological factors
mass extinction
-loss of numerous species in a relatively short period of geological time can also be caused by environmental or biological factprs
how do you measure extinction rates
-extinctions per million species year
E/MSY
-fossils
-pollen cores
-written records
ordovician/silurian
-cold period
-falls in CO2 due to weathering
-loss of marine species
-climate change
devonian extinction
-359 MYA - likely two phases
-no single cause
permian (the great dying)
-250 mya
-two phases = long period
triassic extinction
-200 mya
-poorly understood reasons
-major loss of reptiles, synapsids and conodonts
cretaceous- k/t event
-65 mya
causes asteroid, volcanic, sea level fall and oceanic acidification
volcanic activity
-deccan traps
-65 mya
-massive rise in CO2
carbon cycle and the triassic extinction
-can model the carbon cycle for the planet
-volcanic eruptions heated coal - massively increasing CO2 levels
6th extinction
-cause habitat destruction
-cause global warming
anthropogenic input is increasing
background rates and could be contributing to mass extinction
importance of plants to humans
-environment
-oxygen
-food
-chemicals
-biofuel
-detoxification
how many people are undernourished
870 million
global agriculture by 2050 will need to increase by to meet demands
60-110%
consequences of climate change
-crop loss due to extreme weathering
-changes in rainfall patterns
-decrease crop yield by 50% in next 35 years
enormous progress has been made since 1950
the green revolution saved millions of lives from famine
-initiated by norman borlaug
dwarf plants and yield
-less resources allocated to stem
more to grain development
photoperiod insensitive crops
-in many plants flowering time is determined by seasonal changes in daylength or photoperiod
-photoperiod-insensitive crops can be planted at any time of the year
-serveral harvest cycles are possible
new strategies to ensure food security
-reduction in food waste
- change in consumer behaviour
-changes in farming practices
-improvement of crop cultivars
over 1/3 of food produced
is wasted
meat consumption is bad for environment because
takes up land
use of cover crops
-fast growing annuals
-planted between cash crops to protect and improve teh soil
benefits of cover crops
+reduce erosion
+reduce leaching of N
+green manure
+more on ppt
benefits of tillage
-control weeds
-loosens teh soil
-dries out the soil
benefits of conservation tillage
-reduce soil erosion
-conserve water
-reduce labor and time cost
agroforestry
trees combined with agriculture
precision farming
-using robots to sow seed, identify and exterminate weeds
-modern crop improvement is based on genetics
-marker assisted breeding
-transgenic technology
-gene editing
plant cells are totipotent
-mature plant cells can be induced to give rise to a whole new plant
-most differentiated cells retain this inability
primary metabolites
-carbohydrates
-amino acids
-fatty acids
-cytochromes
-chlorophylls
-intermediates of metabolic pathway
secondary metabolites
-many are involved in plant defences against herbivores or pathogens
huge diversity
-some are toxic
non-vascular plants do not have true
leaves
vascular tissue came first during evolution
-400 mya
-insects and tetrapods were just beginning to colonise land
-early land plants were composed of bifurcating or branching photosynthetic stems
leaves are derived from modified branches
-providing an increased SA for light and CO2 uptake
rubisco is very ineffcient
-slow catalytic activity
-CO2 and O2 compete for the active site of rubisco
when O2 binds to rubisco instead of CO2
wasteful reaction (photorespiration)
CO2 pumps
-in algae and cyanobacteria
-driven by ATP from light reactions
-elevate CO2 in teh cytoplasm
-allows rubisco to favour CO2 over oxygen
modifications of the Calvin cycle
-C4 photosynthesis concentrates CO2 in cells where the Calvin cycle takes place
-CAM also acts to concentrate CO2 and minimises water loss
PUMPs needed in aquatic environments
because CO2 is way below saturation levels
C4 photosynthesis
requires a different cellular organization in leaves
KRANZ ANAYTOMY
C4 photosynthesis
-CO2 is fixed by PEP carboxylase in mesophyll cells
equation on ppt
Malate is transported from
malate is transported from mesophyll cells to bundle sheath cells
advantages of C4 synthesis
-PEP-case is saturated at atmospheric levels of CO2
-ensures iptimal rate of carbon fixation
-CO2 concentration is elevated in bundle sheath cells
crassulacean acid metabolism (CAM)
found in crassulaceae, cacti, bromeliads
-seperation of rubisco, PEPC activity is temporal
the primary root is formed during embryogeneisis
-root present when the plant emerges out of the seed is
lateral roots are formed by branching
from teh primary root
roots have complex cellular structures
-root hairs develop as protuberances from epidermal cells
-they increase the SA for the absorption of water
Rhizoids
single cell filaments
asexual reproduction in roots
some roots form adventitious buds that develop into above ground shoots
-can form horizontal shoots
-roots can form on some fallen leaves
the rhizosphere contains complex microbial communities
that affect the growth of teh plant host
oxygen inhibits
nitrogenase actvity
mycorrhizae =
mutualistic interactions with fungi
phosphobacteria solubilize
teh insoluble phosphorus and converts it into available form
seeds are the _________ food source
primary
seed labelled diagram
-seed coat is outer layer
-embryo is sac in the middle
-at bottom of seed is the food store
seeds are designed for survival
-seeds have low moisture content and almost no metabolic actvity
-they can survive extreme conditions (dehydration/cold/heat/digestion by animals)
-they can persist in the soil for many years UNTIL CONDITIONS BECOME FAVOURABLE
seeds are designed to maximise dispersal
-forceful ejection
-wind dispersal (wings and plumes)
-water dispersal
-dispersal by animals by clinging with hooks and barbs or being sticky
diploid goes through meiosis becomes
haploid
in bryophytes (non-vascular plants) the the dominant form is
gametophytes
in ferns (pterudiohytes) the dominant form is
sporophyte
in seed plants (angiosperms and gymnosperms) teh dominant form is is
the sporophyte (2N)
the female gametophyte (embryo sac) develops within the
ovary
the male gametophyte (pollen) develops within the
anthers
the mother cells in teh pollen sac are parental tissue (2N) they divide by meiosis to give rise to tetrads of microspores which divides into
a vegetative cell and a generative cell this cell has a nucleus which divides into two further male gametes and all three nuclei ,ove down the pollen tube but teh vegatative nucleus degenerates
bryophytes and pteridophytes have
swimming sperm
-rely on moist environments for sexual reproduction
in flowering plants (angiosperms) teh male nucleus is delivered to the ovule by
pollen tubes - no need for moisture
the endosperm develops as a
storage organ
-in arabdopsis it is used up during seed formation to provide energy for development of the embryo
the mature seeds composed of 3 different genotypes
-embryo (2N) = contains predetermined cells, tissues and organs
-endosperm (3N) = contains starch, lipids and or protein reserves
-seed coat or testa (2N , maternal tissue) = barrier that protects the embryo
monocot seeds
seed with a single cotyledon
-seed reserves are stored in the endosperm
dicot seeds
-seed with two cotyledons, endosperms reduced during evolution
-seed reserves are stored in fleshy cotyledons
3 stages of seed development
-embryogenesis
-maturation
-dessication
during the maturation process plants translocate sugars from teh leaves to seeds for storage
as starch or fatty acids
the seed becomes dormant prior to
desiccation
-deeply dormant can’t germinate even in suitable conditions
types of seed dormacy
-physical/seed coat dormancy = impermeable seed coat preventing seed imbibition and embryo unabe to exit a tough seed coat
-physiological = immature embryos, plant hormones
how is dormancy lifted
-time
-favourable environmental conditions (water, light temp and nutrients
-seeds can re-enter dormancy if conditions become unfavourable
seed reserves are mobilised during
germination which is required to support seedling growth
mobilisation of endosperm reserves is controlled by
gibberellin hormones
understanding the control of germination is important
for successful crops
-obtain good germination rates
-avoids pre-harvest sprouting
basic seed enhancement technologies
-quality control = sorting into defined seed size classes or sorting seed density
-polishing off or rubbing of seed coat which facilitates seen imbibition and promotes germination
seed priming
-controlled imbibiton
-just long enough to allow plant to absorb nutrients
-not long enough to trigger germination
-then seeds are dehydrated for storage
seed pelleting
used to alter seed shape, surface properties density and size to enable more precise seedplacement in the soil
seed coating
allows addition of chemicals to protect teh seed from pathogens and/or to improve germination
artificial seed
-somatic embryos are generated using cell culture techniques
-embryos packed into suitable gel matrix and covered with artificial seed coat
-allows clonal propagation of plants
why did Darwin describe flowers an abominable mystery
-because huge levels of diversity
-didnt match slow theory of volution
wind pollinated compared to insect pollinate flowers are likely to be
more dull and no scent
insect/animal pollinated structure
-sticky or barbed pollen grains
-contain FODDER pollen infertile for food only
pollen from wind-pollinated species is
lightweight, small and smooth
getting pollinators attention
-bright colours - bees also see in UV
-nectar or hiney guides to tell insect where togo
-aromas can be carrion-like or dung-like
specialised pollination strategies - entrapment
-water lily look on good notes
mimicry for pollination strategy
look like female wasps can even smell like them
some plants shoot their shot
trigger plant will shoot its pollen at teh insect 15 milliseconds after its triggered
coevolution
interactions between two different species act as selective forces on each other resulting in adaptations that increases their interdependency
cells in each ring know their fate because of their activity of teh ABC
homeotic genes
CYCLODIA gene
expressed asymmetrically in developing flower meristems and buds only in dorsal region
photoperiodism
teh ability to detect changes in day length enables the plant to measure the passing of the seasons and to coordinate aspects of its developemnt to particular times of the year when the conditions are favourable
nightbreaks inhibit flowering
because plants measure the length of DARKNESS
what is a fruit
the seed-bearing structure formed after flowering
TRUE FRUIT
-ovaries expand become fleshy and receptacle is static
false fruit
-ovaries are small and dry forming achenes receptacle expands
apple is a false furit
ovary is retained as teh core receptacle expands and becomes fleshy ovules become the seed
fruit ripening
a series of metabolic and physiological changes in teh fruit to promote seed dispersal]
controlled atmosphere storage of
climacteric fruits
-low temperature
-low O2 reduced respiration
-high CO2
controlled atmosphere storage of
climacteric fruits
-low temperature
-low O2 reduced respiration
-high CO2
ethylene absorbers
use granules to absorb ethylene in cold storage rooms, firmness colr and quality of produce are maintained so reducing waste
function of fruit
-protect the seed during development (embryogenesis)
-seed dispersal - a huge range of mechanisms have evolved using adaptations of various tissues of the flower
some plants are serotinous
= only disperse seeds in response to environmental stimulus
meristematic and callus cells are
totipotent
de-differentiation
reversion of a differentiated cell to an earlier developmental stage
what plant hormone controls grwoth of axillary buds
Auxin
when a plant is wounded the cells may
de-differentiate and bcome callus cells
callus formation occurs due to the hormones
auxin and cytokinin
plant hormones stimulate cell division and differentiation
when a mixture of cytokinin + auxin is applied to callus cells either a root or a shoot will develop depending upon which hormone is higher concentration
-auxins for root development and cytokinin for shoot development
micropropagation
-all regenerated material are clones so very uniform and predicatable growth
-large scale and rapid multiplication of high value or rare plant material
-allows for continous all year round production
-tissue culture is sterile so no bacteria or insect pathogens
somatic embroyos
-plant callus can be reprogrammed to form embryo like structures
artificial seeds
-made from somatic embryos or shoot buds
in vitro breeding interspecific crpsses
-plant breeders use protoplast fusion to cross two sexually incompatible species
-have no cell wlalls
creation of GM plants
disarmed vectors do not produce tumours can be used to regenerate normal plants containing the foreign gene
binary vector system (two plasmids)
-a modified Ti plasmid which has teh air genes required for mobilization and transfer to the plant
-teh binary vector contains only T-DNA right and left border sequences either side of a polylinker for insertion of a foreign gene and a selectable marker
number of leaves and turns is usually
fibonacci. sequence
2/5 = five leaves in two turns
vernalisation =
defined acquisition or acceleration of teh ability to flower by a period of cold
vernalisation indces epigenetic changes in FLC gene
silencing
how does vernalisation silence genes
stable changes in chromatin structure
roots are more sensitive to than shoots to
auxin
photoreversable response
effects of red light pulse can be reversed by immediate exposure to far red
phytochrome is a photoreversable molecule
exits in two forms look on ppt plant responses slide 32
phytochrome undersgoes a conformational change
Pr to Pfr changes its absorption maxima
phytochrome is involved in photoperiodic response
fight for light
-stem elongation or accelerated flowering when red light detected becomes far-red
phytochrome is involved in photoperiodic response
fight for light
-stem elongation or accelerated flowering when red light detected becomes far-red
the tragedy of the commons
teh depletion of a shared resource by individuals acting independently and rationally according to each ones self interest despite teh fact that depleting this resoyurce goes against long term benefits
plant siblings can
recognise each other
population density fo india and china
1.38 billion people Indias population is behind chinas but 1/3 of chinas total land area
what is stress?
-external conditions that adversely affect growth, development and/or productvity
-biotic stress = imposed by other organisms
-abiotic stress = arising from an excess or deficiecy in the physical or chemical environment
heat stress and how to overcome it
stomatal behaviour helps mitigate heat stress
relationship between temperature and stomatal behaviour is complex
optimal temperatures = optimal envaporative cooling
-maximal yields and seed fertility
-extreme highs =if water is available stomatal conductivity (gs) increases
-decreased gs is a water saving strategy
-reduced seed fertility
mechanisms of salinity tolerance
-rapid onset of osmotic stress
-slow onset of ionic stress
quinoa is a facultative halophyte with nutrient rich seeds
-evolved in andes
-bladder cells in leaves and stems (specialised trichomes)
-sequesters Na in vacuoles reduced stomatal aperture
Abscisic acid (ABA) is a major stress hormone
-many similarities in biochemical/metabolic responses to drought cold and salt stress
-other plant processes like dessication of plant tissues (seed maturation)
pleitropic =
having multiple often unrelated effects
