Week 1: How to grow a planet Flashcards
What are the features of life/being alive?
-growth
-respond
-reproduce
-heredity
-homeostasis
-metabolism
-cellular
What is taxonomy?
the science of naming and sorting things
organisms grouped by similarity
What is the taxonomical order?
1.Domain
2. Kingdom
3.Phylum
4.Class
5.Order
6.Family
7.Genus
8.Species
How many domains is there? How do you classify them?
3
Archea= unicellular prokaryotes with isoprene ether lipids
Bacteria= unicellular prokaryotes with fatty ester lipids
Eucarya/Eukaryotes= can be multicellular, have a cell nucleus and membrane bound organelles
How many kingdoms is there?
7
Archea, Bacteria, Protista, Chromista, Fungi, Plantae and Animalie
How do you classify Plantae?
Multicellular autotrophs with chloroplasts and cellulose cell walls.
How do you classify the kingdom of Fungi?
multicellular and unicellular heterotrophs (dont generate their own energy) with chitin cell walls
How do you classify the kingdom of Animalia/Metozoa?
multicellular heterotrophs without a cell wall
they move at least in part of the life cycle
most are bilaterians (left side, right side and a head + gut from mouth to anus)- many phyla of bilateria
What does LUCA stand for?
The Last Universal Common Ancestor
means that all life on Earth descended from a single individual cell which possessed the characteristics shared by all living organisms today.
What did LUCA look like?
DNA
RNA
Protein
Carbohydrates
Membranes, transport proteins
electron transport chains
What is central dogma?
DNA makes RNA makes PROTEIN
transcription translation
DNA= chain of nucleotides formed into double helix
Codons= combinations of 3 nucleotides code for 20 amino acids
RNA= single strand; acts as a “translator” of the DNA code
What are ribosomes?
Convert genetic code into protein sequence
Made of RNA and Protein
used to construct phylogenetic trees
What is the second law of thermodynamics?
All systems tend from a state of order to a state of disorder
Life is a highly ordered process. How can life maintain and reproduce itself?= ENERGY
What is the Urey-Miller Experiment?
experimental simulation conducted in 1953 that attempted to replicate the conditions of Earth ’s early atmosphere and oceans to test whether organic molecules could be created abiogenically, that is, formed from chemical reactions occurring between inorganic molecules thought to be present at the time
What biological molecules are important in life? What chemical elements form them?
1.C02- amino acids- protein- enzymes
2.CH4- sugars- cellulose/chitin- cell walls
3. NH3- fatty acids- phospholipids- membranes
4. SO2- nucleotides- nucleic acid- genetic material
simple chemicals can form complex structures needed for life
What is ATP?
the universal energy currency of the cell
What is chemiosmotic theory?
Peter Michell
the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient
What are reductants and oxidants?
electron donors=reductants
And electron acceptors=oxidants
Reductants are all high energy and chemically reactive
What are chemoautotrophs?
Use chemicals from the environment as reductants – Chemical Energy
e.g. hydrogen
Rely on a world out of equilibrium
reactions must overall be exothermic
What is chrorophyll?
multiple forms a-g
green/purple
absorb blue light and either red or near infrared
then light energy is turned into chemical (redox) energy in reaction centres
What are reaction centres? What do they do? What is their structure?
Structure:
-have a core which is made of two polypeptides
-where these bind together is a so-called “special pair” of chlorophylls. These are special because, when they absorb light they are liable to lose an electron.
How:
The electron is transfered through the protein to a quinone, producing an oxidised chloropyhyll (Chl+) and a reduced quinone (Q-). This electron transfer is the step where light energy gets converted into chemical energy. We call this charge separation.
What are the 2 forms of reaction centres?
Type I and Type II
Where are Type I reaction centres found?
green sulphur bacteria and in the heliobacteria
Where are Type II reaction centres found?
green non-sulphur bacteria and in purple sulphur bacteria.
What are the differences and similarities between Type I and type II reaction centres? Why are they different?
similarities:
two types have the same core structure but differ in way electrons arrive and leave
differences:
Type I, electrons are passed from the reaction centre quinone to a so-called iron-sulphur protein (Fe-S) such as ferredoxin, which is soluble.
In Type II reaction centres, the quinone itself leaves the reaction centre, carrying electrons away in the membrane
WHY:
Type I and Type II reaction centres evolved in distinct evolutionary lines - that is one ancestor photosynthetic organism separated into 2 species
it is though in two distinct bacterial lineages.
How can genes move laterally?
genes can move laterally from one species to another, without sexual reproduction occurring.
This may result from a cell breaking open, releasing DNA, and that DNA being absorbed by another species.
or It may occur in a more directed way, with direct transfer of DNA from one organism to another.
How did one group of bacteria find to have both types of reaction centres?
somewhere between 3.5 and 3 million years ago, an organism arose that had both a Type I and a Type II reaction centre through lateral gene trasnfer.
What were the implications of having both reaction centres Type I and Type II?
both reaction centres were able to work in series, with electrons for one being passed to the other ( Type II to Type I).
This combined system was able to create a bigger energy difference between the starting electron donor and the end acceptor.
The key acceptor in this system is carbon dioxide, which is reduced to form sugar.
The new electron donor which emerged was one of the most abundant molecules around - water.
These new cells evolved the ability to split water into electrons and protons, producing oxygen as a bi-product (photolysis)
What was the organism that evolved to have both reaction centres?
cyanobacterium
What are the advantages of having both reaction centres?
all organisms that have both types of centre are able to evolve oxygen and visa versa.
How do we know when cyanobacteria appeared?
3-2.4Ga
Evidence comes from geological deposits
1. stromatolites
2. distinct bands of oxidised iron and other metals in sedimentary rocks
What were the impacts of Oxygen?
-Global Cooling= As oxygen was released into the atmosphere, it stated to react with this methane, producing CO2- plunged into an ice age considered to be the first and longest major glaciation event (Huronian glaciation)
-Reactive Oxygen= When oxygen first appeared in the atmosphere, cells had not yet evolved defences against them. For organisms that have never been exposed to oxygen, so-called anaerobes, oxygen is deadly.
+Ozone= When molecular oxygen absorbs UV, the bond between the two O atoms is broken, releasing atomic oxygen, atomic oxygen is a free radical and highly reactive, but what it mostly reacts with in the atmosphere is molecular oxygen= ozone
+Oxidative Phosphorylation= cells which evolved to use their “food” more efficiently, meaning that they are able to grow bigger. Bigger cells have other advantages, notably that some cells learnt how to “eat” smaller cells.
Key moments in geological time scale of Earth?
1.4550Ma= formation of Earth
2.4527Ma= Formation of Moon
3. 4000Ma= End of the Late Heavy Bombardment of Life
4. 3200Ma= Earliest start of photosynthesis
5. 2300Ma= Atmosphere becomes oxygen rich, first Snowball Earth
6. 750-635Ma= The Snowball Earths
7. 530Ma= Cambrian explosion
8. 380Ma= first vertebrate land animals
9. 230-66Ma= non-avian dinosaurs
10. 2Ma= first hominins
Order of organisms groups formation in geological time scale?
1.Prokaryotes
2.Eukaryotes
3.Multicellular life
4.Animals
5.Land plants
6.Mammals
7.Hominins
What are the 4 Eons?
Hadean 4600-4000
Archean 4000-2500
Proterozoic 2500-540
Phanerozoic 540-today
When did complex life (animals, plants and fungi) begin to exist?
In the phanerozoic period (540-today)
What happened to oxygen levels in the proterozoic? How do we know this?
photosynthesis led to an accumulation of atmospheric O2 at Great Oxygenation Event
however modern levels were not reached until the end of Proterozoic.
EVIDENCE:
1.chemistry to try and reconstruct the levels of oxygen
2.look at geology in terms of banded iron formations
What were the Proterozoic glaciations? Name? When?
Gaskier’s glaciation
580 million years ago, (about 9 my before the appearance of large Ediacaran fossils)
Widespread glaciation deposits toward end of Proterozoic
When did large fossils turn up in geological record?
Ediacaran
Large organisms first appear in the Ediacaran fossil biota
After a long period of relative stasis, large fossils turn up in the Ediacaran deposits in Newfoundland, Australia, Russia, and UK
What are fronds?
Ediacaran fossils
-Variety of different morphologies with branching structures
-Some lay flat on sea floor surface, some attach via a holdfast
-Similar fundamental morphologies, but different sizes and shapes
-They undergo the same patterns of fractal growth
What are Rangeomorphs?
Clade of the frond taxa
Rangeomorphs are weird fractally growing fronds and are hard to characterise
-The frond taxa are fundamentally similar in their morphology and fractal growth, just differ slightly in their proportions and patterns
-They can’t be plants because the environment is too deep: no light= no photosynthesis
-unlikely to be proper animals given anatomy and asexual reproduction
-unique and weird
What are bilaterians?
Ediacaran fossils
-these taxa have different sizes and shapes but fundamental similarities in their constructions: a ‘head’, and a left side and a right side
-the symmetry is not classically bilaterian, it is ‘glide’ symmetry.
Examples: Dickinsonia and Kimberella
What were some of the Ediacaran fossils?
‘Frond’ taxa:
-similar fundamental morphology and fractal growth but different sizes and shapes with branching structures
-some lay flat on sea floor surface some attach via a holdfast
-they likely form a ‘clade’=rangeomorphs
-cant be plants as environment too deep (no light=no photosynthesis)
-unlikely to be proper animals given anatomy and asexual reproduction
“Bilaterians taxa:
-have different sizes and shapes but fundamental similarities in their construction ( a head and a left side and right side
-the symmetry was not classically bilaterian, it is ‘glide’ symmetry
Ediacaran animals?
-Dickinsonia left traces of footprints indicating it was digesting the underlying microbial mat this is consistent with osmotrophy. Also been found to composed of animal like molecules (like cholesteroids)
-Kimberella leaves mollusc style feeding grazing traces
-some Ediacaran taxa show evidence of muscle fibres=movement
-traces of tiny burrows at end of Ediacaran= possible movement
What is the evidence for possible Ediacaran animals?
Some Ediacaran organisms appear to be candidates for the first animals given their anatomy, composition, and behaviour:
-Dickinsonia leaves traces of ‘footprints’ indicating it was digesting the underlying microbial mat
(This is consistent with osmotrophy, as is their high surface area)
-Dickinsonia has also been demonstrated to be composed of animal like molecules
(Gas chromatography of organic remnants shows evidence of animal-like cholesteroids and not typically algae lipid biomarkers)
-Kimberella leaves mollusc style feeding grazing traces (suggests kimberella was an animal?)
-Some Ediacaran taxa show evidence of muscle fibres, therefore movement
-Traces of tiny burrows at the very end of the Ediacaran, possible movement
What are the possible Ediacaran Triggers? Why did large fossils appear in the fossil record during this time after long period of stasis?
1.Deglaciation:
-Gaskier’s Glaciation was about 9 my before the appearance of large Ediacaran fossils
-However there had been many previous glaciations :‘snowball earth’ so doubts
2.Oxygen:
-increasing atmospheric oxygen may have facilitated evolution of larger body sizes in the Ediacaran.
-increased tectonic activity could have led to more oxygen
-All Ediacaran organisms appear to have very high-surface area to volume ratios, important for gaseous exchange
- Carbon Excursion:
-massive Shuram Carbon Isotope Excursion occurs in the Ediacaran
What is the classification of animals as bilaterians?
-they have a left/right sides
-head and tail
-top and bottom
-gut from mouth to anus
-many phyla of bilateria
When did large organisms first appear?
in the Ediacaran fossil biota
-including candidates for the first animals given their anatomy, composition and behaviour
What is a phylum? Examples?
A unique body plan
There are around 30 modern animal phyla: most are bilaterians
E.g.:
Arthopoda:
-bilaterians with jointed appendages (insects, crustaceans, spiders, scorpions and millipedes)
Chordata:
-bilaterians with notochord and dorsal nerve cord (tunicates, lancelets and all vertebrates)
What is a phylogeny?
an evolutionary tree
-hypothesis of evolutionary history and relationships between species
-branch length= amount of evolutionary change
What is molecular phylogeny?
-based on similarities and differences in genetic sequences
-built using computer algorithms
-ancient fossils don’t have DNA so we need to use morphological data instead
What is a crown group? (phylogeny)
all living members of a clade, its common ancestor and all descendants
(can be applied to all trophic levels)
What is the stem group?
extinct organisms outside that group on the lineage to that most recent common ancestor
(can be applied to all trophic levels)
What is superphyla?
groupings of phyla
What are the 3 superphyla of bilaterian animals?
- Lophotrochozoa (molluscs, annelids and lots of other phyla)
- Ecdysoszoa (arthopods and allied phyla)
- Deuterostomes (chordates inc. vertebrates and echinoderms)
What defines the beginning of the Cambrian?
The trace fossil Treptichnus (a worm burrow)
What fossil are suddenly abundant and diverse in the Cambrian?
The fossil anthropods Trilobites
What is the Burgess Shale?
A middle Cambrian fossil deposit in Canada with exceptionally sot tissue preservation.
Preservation of the Burgess Shale?
The marine community was buried rapidly following collapse of a sea cliff
Sediment accumulated and underwent diagenesis preserving soft tissues as clays
Whole community preserved not just shells and hard bits.
Fossil taxa from the Burgess Shale?
- Anomalocaris:
-large compound eyes, raptorial appendages and swimming flaps
2.Hallucigenia:
-worms with stubby walking legs and very unusual anatomies
3.Brachiopods:
-sessile filter feeding organisms with front and back ‘shells’
many of these are interpreted as stem groups of modern taxa
What is meant by the Cambrian explosion?
-most animal phyla first appear for the first time in a sudden burst of diversity
-very few phyla have a later origin
-the diverse and disparate body plans of animals were therefore established in a very small period of time (at beginning of Cambrian or earlier)
-over period of a few million years
-evolution was 5x faster than normal during Cambrian
What are the possible causes of Cambrian explosion?
complex interplay of biological and geological factors
1. Biological
-more complex ecological interactions (predator-prey relationships)
-earlier on when there is no competition and no constraints lots of different body plans might originate using same developmental mechanisms
- Geological:
-arrangements of continents changed at beginning of Cambrian (breakup of Rodina supercontinent)= lots of exposed shelf
-large amount of exposed continental rock= more weathering= more carbonate input into oceans= increased ocean alkalinity
Comparison of Ediacaran Ecosystems and Cambrian Ecosystems and Modern Ecosystems.
Ediacaran:
-two dimensional microbial mat surface
-organisms are mostly sessile and live on that falt surface
-no burrowing or swimming
Cambrian:
-burrowing and mixing of layers, penetration of oxygen
-some filter feeders, some swimmers, some predators
-more three dimensional
Modern:
-much more complex
-organisms occupy a broader range of lifestyles, diets and interactions.
What were the Ordovician reefs?
-shift from microbial dominated environments to reef type env
-corals and sponges dominate creating rocky reef environments: important geologically and biologically.
What are sponges?
Reef builders
-in the phylum Porifera
-very simple animals
-simple tissues
-no symmetry
-filter feed with ciliary action (Choanocytes)
What are corals?
-reef builder
-anthozoans
-sessile cnidarians
-form a mutualism with photosynthesising algae (zooxanthellae)
-comprised of solitary or colonial polyps often housed in or on a mineralized skeleton
What are ordovician reef builders?
Palaezoic fossil corals:
-Rugose corals= mostly solitary known as horn corals
-Tabulate corals= colonial with hexagonal cells and partitions
What are ordovician reef inhabitants?
Crinoids=
-sea lilies
-filter feeding
-with stalks
Cephalopods:
-predatory swimming molluscs
-muscular arms
brachiopods (phylum)=
-sessile
-filter feeders
-front and back valves
Trilobites=
-arthropods
-3 part exoskeleton
-varied diets (scavengers, predators…)
What are autotrophs?
generate energy and organic matter from sunlight
(photosynthesise)
What are herbivores/Primary consumers?
consume the primary producers
through grazing, filter feeding etc.
What are carnivores?
consume the herbivores
What are omnivores?
consume primary producers and herbivores
What are apex predators
only consume carnivores, at the top of the chain
(dont think this is quite right but that’s what he put)
What are food webs
shows the feeding relationships
energy lost at each stage
most matter is primary producers
What happened to the diversity of trophic levels during the Ordovician?
increasing diversity of primary producers in the Lower Ordovician
increasing diversity of consumers in the Middle Ordovician
What are phytoplankton?
-autotrophs
-modern phtoplankton= cyanobacteria and various eukaryotic alage
ordovician phytoplankton:
-acritarchs
-organic walled microfossils of unknown affinity
What are zooplankton?
-heterotrophs
-diverse organisms including tiny arthopods, jellyfish and juvenile molluscs.
What is the Great Ordovician Biodiversification Event
big increase in number of animal families (marine) occurred in the Palaeozoic= Great Ordovician Biodiversification Event.
What is Sepkoski’s Curve?
Compilation of fossil data for Phanerozoic which shows pattern of originations and major extinctions
What did ordovician earth look like?
-splitting of supercontinents
-massive volcanic activity (mantle superplume)
-global warming= high sea level and large shelf area
-Strontium excursion
-All of this is conducive to phytoplankton radiation and thus global biodiversification
Extra terrestial input in the Ordovician
-global record of megabreccias and chondrites in the Middle Ordovician
-period of heavy meteorite bombardment during that time
-possible link is not very clear
What happened at the end of the Ordovician?
-first of the ‘big five’ mass extinction events
-it was actually two pulses of extinction close together in time
First pulse:
-related to global cooling, massive glaciation and drop in sea level
Second pulse:
-related to changing ocean cycles and widespread anoxia, warming again
What is an odd sounding experiment?
acoustic enrichment might help reef communities recover
What is coral bleaching?
When temperatures rise, coral bleaching occurs whereby the coral expel their zooxanthellae algae.
What are the 3 superphyla of bilaterian animals?
1.Lophotrochozoa (molluscs, annelids and lots of other phyla)
2.Ecdysozoa (arthropods & allied phyla)
3.Deuterostomes (chordates inc. vertebrates, and echinoderms)
What are chordates?
A phylum
Chordates have:
-notochord- stiff rod along the ack
-dorsal never cord
-pharyngeal slits (for breathing)
These are synamorphies= unique defining characteristics
What are vertebrates?
-in the phylum Chordata
have all the chordate characteristics plus:
-segmented brain
-medial fins
-branchial arches
-paired eyes, olfactory bulbs and ears
Two types
Jawless (agnathans)
Vertebrate clades:
1.Lampreys
2.Hagfish
Jawed (gnathostomes):
-jaws
-teeth
-mineralized bone
-paired appendages
Vertebrate clades
1. Chondrichthyes (cartilaginous fishes)
2. Actinops (ray finned fishes)
3.Sarcops (lobe finned fishes)= us
Animal development
- Start with a zygote (fertilised egg)
- undergoes a process of cleavage
- changes into a blastula
- undergoes a process of gastrulation
- becomes beginning of a “tube” with ectoderm, gut and endoderm
- may become distinguished with having a head and a tail
- appendages may then form=larvae
What are hox genes?
-as the animals develop they develop hox genes
-expressed in different regions of the body
-this specifies the type of anatomy in taht region
-hox genes are arranged on chromosomes
VERTEBRATES HAVE MULTIPLE COPIES OF EACH HOX GENE (gene duplication)
Development of appendages?
gene expression patterns also determine where and how appendages develop
-In vertebrate limbs sonic hedgehog specifies digit identity e.g. fingers.
What are Cambrian Vertebrates?
Metaspriggina
-vertebrate stem group
A Cambrian stem vertebrates from the Burgess Shale with paired eyes and branchial arches (gills)
What are Ordovician Vertebrates?
Sacabambaspis
-vertebrate crown group
An Ordovician jawless fish with a boney dermoskeleton and paired nostrils
What are Silurian vertebrates?
Ostracoderms= armoured jawless fish
-diverse dominant vertebrates in the Silurian
-they are stem-gnathostomes
e.g. Cephalaspis
-paired fins but a lamprey like brain and single
nostril opening
What are Devonian Vertebrates?
Placoderms= originated in the Silurian but diversified and dominated in Devonian
-stem-gnathostomes
-armoured jawed fish
-biting jaws, primitive teeth and pelvic appendages
e.g. first mega predators like Dunkleosteus
-had extra- ordinary biomechanical biting
strength: 5000 Newtons (stronger than a great
white shark)
-6m long
What is the Devonian Nekton revolution?
occupation of the deep water column
Large Devonian swimming predators is another advance in ecological complexity
From simple flat Ediacaran ecosystems, burrowing Cambrian ecosystems, planktonic Ordovician ecosystems, to the Devonian Nekton revolution
Devonian decline and extinction
ostracoderms undergo slow extinction:
-collision of NA and EU to form Euramerica continent so ostracoderms were restricted to shallow water environments
-however recently hypothesised that ostracoderms may have been predated to extinction by jawed vertebrates= evidence of bite marks
jawed vertebrates also suffer at late Devonian extinction event
How and when did animals move onto land?
Animals originated and diversified in the marine realm
At some point they moved into the terrestrial realm
Devonian
What are the first animals to invade land?
Arthropods:
1. millipedes in Ordovician
2. then arachnids and hexapods in Devonian
3. vertebrates invaded later in Middle/Upper Devonian
What are terrestrial anthropods and vertebrates?
Arachnida: Spiders and Scorpions
-Arthropods with 8 legs, chelicerae jaws
Hexapoda: Insects and friends
-Arthropods with 6 legs, head, thorax, abdomen
Tetrapoda: amphibians, reptiles (including birds), and mammals
-Vertebrates with 4 limbs with digits
What are the marine relatives of the Arachnids?
Trilobites were walking in marine environments from the Cambrian onwards
Sea spiders are not arachnids, but in the same group (Chelicerata)
Horseshoe crabs are marine chelicerates that can walk and breath on land
What are the hexapods?
Molecular phylogenetics revealed that insects actually evolved from within crustaceans. Not predicted from morphology and taxonomy
Enigmatic blind marine crustaceans are sister group to Hexapoda
Basal hexapods are completely terrestrial and flightless e.g. springtails, silverfish
What are the lobe finned fish?
Tetrapoda truly terrestrial ‘fishes’ with 4 feet
Coelacanths are an ancient deep marine fish lineage, rediscovered
Lungfishes live in freshwater, can breathe air, and use fins to ‘walk
What are arthropod trace fossils?
Trace fossils (ichnofossils) are indirect evidence of past life (e.g. burrows, trackways etc.)
Diplichnites is an arthropod trace fossil trackway from the Middle Ordovician of the Lake District UK.
-this is the earliest evidence of an animal in a truly terrestrial environment
-most likely a millipeded
(first body fossils of millipedes don’t show up until later in the Silurian)
What is the Rhynie Chert?
The Rhynie Chert is an unusual Early Devonian terrestrial deposit preserving plants and animals in fine detail
Geyer/volcanic hot springs preserved the ecosystem through silification
Early arachnids and first hexapods fossils found here
What are terrestrial arachnids?
Trigonotarbids are early arachnids with book lungs indicating air breathing
also more advanced mites
What are the first hexapods?
Fossil springtales in the Rhynie chert are the first unequivocal hexapods. They are flightless
The Rhynie chert also yields the first true insect, which likely had wings
What is Tiktaalik?
Tiktaalik is a key transitional fossil from the Upper Devonian of Canadian arctic
Important mix of early Sarcopterygian and tetrapod characteristics:
-Enlarged humerus bone would have supported more weight for walking
-Enlarged snout and flexible neck would have enabled living near waters edge and breathing
What changed during the tetrapod transition?
whole suite of fossil lobe-finned fish revealing the stepwise acquisition of tetrapod characters and transition to terrestrial habitat
Changes in:
-limbs
-shoulders
-ribs
-head
-fins
-appearance of first digits
Where are the earliest Tetrapod walking traces found? What is the evidence?
Found in Middle Devonian of Poland
Some 18million years before first body fossil evidence of tetrapods
EVIDENCE
-alternating limb movement no drag
-digits in the footprints
What are molecular clocks?
based on a molecular phylogeny with fossils
give early estimates for millipedes on land (Cambrian) Silurian for arachnids and hexapods
What changes in physiology occurred when invading land?
transition from marine to terrestrial brings challenges in regulation and coping with environmental changes:
1.homeostasis= maintaining a steady internal state
2.breathing= air rather than water is a challenge with different solutions. (developed spiracles, trachea, lungs etc)
What occurred to arthropods during the Carboniferous? Why?
Upper Carboniferous arthropods reach giant sizes
WHY?
-corresponds with maximum oxygen levels in Phanerozoic
-Body size could be related to oxygen given the passive breathing system of hexapods and millipedes
-air diffuses through trachea and spiracles
How did early terrestial breeding occur?
Terrestrial breeding often means internal fertilization. Modified legs in male millipedes transfer sperm
How did body structures change from water to land?
Sensory structures change from water to air, for example hearing in tetrapods
Reduction of fin rays, increasing strength of digits and other bones for carrying weight whilst walking
How do arthopods and tetrapods support their weight on land?
Arthropods have exoskeleton
Tetrapods have endoskeleton
Both have muscle pairs working for flexion and extension of legs
What were the ecological changes following terrestrialization of animals?
Following the invasion and diversification of bacteria and plants on land, there will have been unoccupied niches on land
The first terrestrial herbivores would have faced little challenges and thrived, same for first terrestrial carnivores
What are the problems and adaptations with being a byrophyte?
-Poor ability to capture and retain water=confined to damp places
BUT
+ can spread using spores
-Poor water transport
-Limited uptake of nutrients (maybe ombrotrophic)
BUT
+Can survive total desiccation (resurrection plant)
-Limited height – need to be near surface
