Evolutions of the Major Groups of Organisms PDF

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Summary

The Major Groups of OrganismsSpecies formation – Speciation Change within a lineage  Formation of new lineages (associated with split of existing lineage)  Organisms exist in discrete clusters – no intermediate forms of modern plants and animalsSpeciation Historically structures were argued abou...

Description

The Major Groups of Organisms Species formation – Speciation   

Change within a lineage Formation of new lineages (associated with split of existing lineage) Organisms exist in discrete clusters – no intermediate forms of modern plants and animals

Speciation  

Historically structures were argued about – this is how we classified – according to features Lineage formation leads to the diversity of life

How Many Major Kinds of Organisms?      

Founding father of classification (Carolus Linnaeus (1707-1778)) 2 Kingdoms of Organisms A 3rd Kingdom of non-organisms Animals, Plants & Minerals Mid-1800s: John Hogg & Ernst Haeckel - Haeckel removed minerals R.H. Whittaker - 1969 - 5 Kingdoms - Bacteria, Protists, Fungi, Plants & Animals

How Many Major Kinds of Organisms? 

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3 domains - Domain Bacteria - Domain Archaea - Domain Eucarya Increasing emphasis on comparisons of genes on the molecular level (initially ribosomal RNA genes) as the primary factor in classification - Genetic similarity was stressed over appearances and behaviour

The Tree of Life 

A tree with just the major groups of protists, plants & animals

Kingdom Plantae  

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The earliest land-plant fossils date back to the Ordovician period, 443-489 MYBP It’s been argued that land plants evolved through the coming together of: - A green alga (Kingdom Protoctista) - A fungus, with the alga being dominant - I.e. a symbiosis (mutualism) Alga + fungi seems plausible: - Plants have several fungus-like characteristics - E.g. pollen tubes are very fungus-like & many cells in plants grow intrusively into tissues, rather like parasitic fungi. Kingdom Plantae - Land plants most likely evolved from a green algal ancestor alone in the intertidal zone

Evolution of Land Plants 

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Whatever the ancestor, land plants eventually developed and structures to id this appeared - Gas exchange pores, i.e. stomata - Stomata open to allow carbon dioxide to enter a leaf and water vapour to leave A vascular system (= a ‘plumbing system’) - Linear arrangements of liquid-conducting cells Xylem & phloem - These cells conduct water & food & provide mechanical support Kingdom Plantae – evolution of land plants - Vascular System allowed plants to become big - But lignin deposits (mainly in vascular system) allowed them to become even bigger Cuticle - A waxy waterproofing - Reduces water loss Spores - Packet of undifferentiated cells - Poorly provisioned - Some terrestrial plants developed seeds - A major advance on spores as the means of dispersal of progeny Seeds - Packet of differentiated cells (embryo) - Well provisioned with nutrients for long-distance travel & survival in adverse conditions - Travel (= dispersal) is assisted by animals in some groups Mainly evolved in response to the need to: - Maximise light (photon) capture: foliage - Maximise water & nutrient capture: roots - Provide anchorage: roots Different plants achieved different solutions to these problems Hence the great diversity in plant architecture

Other Factors Influencing Plant Architecture

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Extremes of climate (cold, wind, dryness) Need for H2O conservation Physical defence against herbivores

Dominance of Angiosperms        

The currently dominant plant group is the Angiospermae - but that wasn’t always the case The angiosperms flourished from the Cretaceous onwards One hypothesis argues that they were able to radiate / diversify behind a ‘biochemical shield’ A diverse chemical ‘armoury’ to defend against attack by herbivores such as dinosaurs & insects Armoury consists of defensive chemicals, e.g. alkaloids, tannins, mustard oils &c Angiosperms, compared with other types, tend to be faster-growing Many have developed highly efficient pollination systems involving animals such as insects Insects were themselves becoming very numerous & diverse by the tertiary

Kingdom Fungi   

There has been considerable debate over fungal origins rRNA tells us that they are more closely related to animals than plants - Heterotrophic, feeding on organic material originally synthesised by plants Plants are autotrophic

Kingdom Animalia   

The various phyla The Burgess Shale in British Columbia, Canada Superbly preserved fossils of many animal phyla

Evolution of Animals    

Phyla were present in the Cambrian period Body plans are very different Body plan – the ways in which the body cavity + organs + appendages + supporting structures + nervous / sensory systems are organised These are linked to locomotion, feeding & defence

Cambrian Period 

Sponges

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Brachiopods Comb jellies Jellyfish Molluscs Worms Jointed-limbed animals (arthropods) Other invertebrates (animals lacking backbones) were present

Sponges: Porifera       

The most basal of the truly multicellular animals (metazoans) Evolved from single-celled protists These protists resembled the extant protist group choanoflagellates Choano – Greek word for ‘funnel’ Some choanoflagellates are colonial Coloniality led to true multicellularity This enabled more efficient (particulate) food gathering

Cnidaria: Hydroids, Jellyfish, Sea Anemones, Corals    

Sponges have one germ layer and lack true tissue organisation Endoderm allows cnidaria to develop tissue Basic ‘sac’ body plan Digestive cavity (W) is a hydrostatic skeleton - can work only because the body wall (ectoderm + endoderm) is very thin

Evolution of Animals  

Triploblastic animals: ectoderm + mesoderm + endoderm 2 groups of triploblasts Protostomes & Deuterostomes ‘Tube’ body plan in most cases – separate mouth & anus The origin of painful piles

Embryo 

The blastula is a hollow ball of cells that forms in early embryonic development

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Some cells form an invagination (into the blastula’s cavity) to form the future gut –the invagination’s opening is the blastopore This blastopore eventually forms the mouth of protostomes – It forms the anus of deuterostomes Protosomes & deuterostomes differ with respect to embryology: cleavage Cleavage is determinate in protostomes Is indeterminate in deuterostomes – the cells’ fates are not fixed – are ‘stem cells’

Becoming Bilateral        

Those animals having bilateral symmetry as well as triplobastic arrangement of tissues Ps + some Ds – i.e. not a monophyletic grouping Associated with bilateral symmetry is cephalisation – the formation of a head end What’s the ‘purpose’ / function of a head? The mouth is likely to be the leading end of the animal as it moves Feeding-related sense organs are best suited near the mouth Concentration of nervous tissue (ganglion, brain) best sited nearby Mouth & sense organs are best suited away from region where waste materials (e.g. faeces) are expelled (i.e. anus)

Locomotion in Bilateria 

Locomotion type & efficiency: linked to tissue arrangement

Locomotion   

Flatworms & ribbon-worms: have a bulky layer of mesoderm Mesoderm highly compressible – dissipates mechanical forces, & so little force is transmitted to the gut cavity This body plan is OK for creeping (with the aid of a body covering of cilia) + slow swimming (peristalsis: waves of contraction along body)

Annelids 

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True worms e.g. earthworms - Fluid-filled coelom (a secondarily produced cavity within mesoderm) - Body is segmented (rings: ‘annelus’ = little ring) - Segments are separated within by bulkheads/partitions (septa) - Rings’ muscles + septa improve mechanical efficiency of peristalsis Importance of the septa - Pressure changes in one part of the body are not dissipated along the rest of the body Appendages: paddles with chetae (= bristles) - Annelids include burrowers and swimmers

Nematodes (Roundworms)  

Have a persistent embryonic cavity – the pseudocoelom (fluid-filled) Nematodes move by whip-like movements due to: - Contraction/relaxation of longitudinal muscles working vs the pseudocoelom (= a hydrostatic skeleton) - Stiff body cuticle - Nematodes are not capable of much directional control

Arthropods evolved from an annelid-like ancestor    

Visualise annelid worm’s ‘paddles’ becoming jointed limbs Series of jointed appendages (ancestrally on all segments) – good directional & positional control But for a terrestrial existence, the limbs + body wall need to be strong Note that the Annelida were definitely not the ancestors of the Arthropoda – new lineage formed

Arthropods      

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Rigid, tubular exoskeleton Rigidity due to mineralisation (calcium salts) in Crustacea only Sclerotisation (phenolic compounds) Crustacea, insects, myriapods, arachnids) Crustaceans are the dominant marine arthropods Their segmented bodies are divided into three regions (head, thorax, abdomen) with different, specialized appendages in each region The jointed appendages of ancestral arthropod became modified (= differentiated) , from structures used only for crawling / walking, into: - Antennae (feel / taste / smell) mouthparts - Prey capture/food handling devices (claws) - Gill-bearing structures (crustaceans) - Egg-laying devices (insects) - Propulsive devices (crustaceans) - Silk-spinning (spiders) Insects also evolved wings Flight is obviously one key to the great success of insects Flattened lateral extensions of the thorax In aquatic insects – helping windassisted dispersal across water surface? Waterproofing of the body covering - Mineralisation & sclerotisation in Crustacea affords little protection vs water loss - Terrestrial Crustacea are mainly confined to damp places (e.g. woodlice) Animalia: Arthropods - Insects, spiders, scorpions & co. far less restricted - Because of combination of sclerotisation + lipids (inc. outer coating of wax)

Arthropod Eyes 

Cambrian explosion and the eye - Evolution of eyes played a key role in the massive diversification of animals that undoubtedly began in the Precambrian but became evident (fossils) by the Cambrian - Anomolocaris & predatory trilobites had compound eyes - Visual predators - Provided strong selection pressure upon prey - To evolve hard body parts, e.g. arthropod exoskeleton, mollusc shell, marine worm bristles - To develop a burrowing habit - Change / modify modes of locomotion - To evolve eyes themselves - Parker argues that the evolution of the compound eye by Precambrian proto-trilobites ‘kick-started’ the Cambrian ‘explosion’

Evolution of the eye   

Compound eyes occur in polychaete annelids, but are most developed in arthropods Evolution of the eye Eyes range from the simple to the compound Simple eyes: e.g. spiders, & atop the insect headIn jumping spiders (predatory), simple eyes can be focused to form an accurate image - Excellent vision, with among the highest acuities in invertebrates – it helps to have 8 eyes - The brain of a jumping spider includes a comparatively large region for visual processing

Compound Eyes     

Repeating units of ommatidia, each of which functions as a separate visual receptor 3000-9000 ommatidia found in many insects, and 25,000 found in each eye of fast moving animals Form a mosaic ‘image’ ‘Eyes can provide very wide visual range, 360o in some cases 25,000 ommatidia c.f. bees (3-9,000) found in each eye of fast moving animals – e.g. dragonfly

Silk Production    

Silk is a protein fibre which is ductile – i.e. can be stretched considerably Secreted by organs - spinnerets in spiders & salivary glands in insect caterpillars Used mainly in prey capture by spiders, & as protection vs natural enemies/adverse abiotic factors by insects Silk production has been a key factor in the success of spiders

Flight Capability

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A key to the success of insects The vast majority of insects are winged as adults Helped them to exploit new habitats & foods Some small spider spp. can fly! They ‘balloon’, i.e. release silk which is then caught by a breeze – is important in their dispersal / colonisation of new habitats Darwin observed ballooning spiders 100 km away from S. American mainland

Loss of flight capability   

Fleas, Lice, Bedbugs All evolved from winged ancestors, but then lost their wings Winglessness is usually an adaptation to a parasitic lifestyle

The pupal stage in insects  

Enabled larval & adult stages to occupy different niches Thereby avoid competition between larvae & adults

Molluscs      

Appearance of calcareous shell Coincided with trebling of calcium levels in seawater due to tectonic/volcanic activity (in Cambrian) Shell is an exoskeleton: providing support + defence vs predation Is secreted by specialised organ – the mantle Muscular ‘foot’ for locomotion or prey capture The shell was subsequently reduced, used for buoyancy, or even lost in some molluscs

The mollusc radula (feeding)    

An array (a ‘mat’) of horny protuberances (‘teeth’), used to rasp away at algae, leaves Absent in bivalves (oysters, clams &c) Worn / broken teeth are replaced by new ones (moving ‘belt’ of teeth) In addition, a horny beak is used for biting in some groups (cephalopods)

Mollusc eyes 1. 2. 3. 

A cup containing light-sensitive cells (pinhole eye) e.g. Nautilus A cup, backed by a mirror (scallop) A camera-like device (snail, squid) Useful for detecting movement, of predators / prey

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Cuttlefish, squid & octopus can judge distances & perceive colour The eye of Giant Squid is c.30cm (1 ft) in diameter

Echinoderms  

Spiny-skinned animals: sea urchins, starfish, and their allies Radially (as opposed to bilaterally) symmetrical

The Emergence of the Vertebrates   

Animals with internal backbone that encloses dorsal, hollow nerve cord (they are a group of chordates) The first vertebrates undoubtedly evolved from a chordate, resembling ‘Amphioxus’ (= Branchiostoma), the ‘lancelet’ The lancelet like-ancestor itself arose from a tadpole-like animal with: - A recognisable head - A flexible (elastic) rod-like structure (notochord – a ‘proto-backbone’) along its back - A series of gill slits for filter-feeding

Organisation of the nervous system 

Linked to body plan: - Longitudinal nerve cord (linked to bilateralism) - Brain (linked to cephalisation) - Segmental ganglia (linked to segmentation / bilaterality)

The origin of backache    

Dorsal nerve cord is enclosed by cartilaginous or bony spinal column In locomotion, the muscles act against the spinal column The notochord has become the intervertebral discs These act as a shock absorbers + flexible links between vertebrae

First Fishes   

Jawless A later, extant jawless fish – the lamprey A delicacy several centuries ago

Jawed Fishes    

Cartilaginous They possessed jaws - developed from gill arches (previously used only as support for gills) Jaws used for feeding on large-sized animal prey The armour of early fishes was made of dentine tubercles (even extant sharks have these)

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Tubercles became more pronounced around & in the mouth to form teeth Dentine is a calcified tissue

Bony (Ray-Finned) Fishes    

Cartilage in skeleton largely replaced by bone A major advance in positional control Whole-body movements not always required () Enables massive diversification in body shape

The swim bladder    

An advance in terms of bouyancy & its regulation Sharks & close relatives (cartilaginous) can adjust bouyancy (liver oil content) to a v. limited degree (slow) But bony fish do it very well – they employ the swim bladder (rapid) They control the amount of gas in the bladder – releasing gas into / absorbing gas from the bladder’s interior

The lateral line system   

A sensory system that detects movement + vibrations (+ in some fishes, electrical impulses) Hair cells are similar to those in higher vertebrate inner ear (homologous) Used to avoid collision (inc. in shoals) & predation, detect prey, enable orientation

Colonisation of the land by Vertebrates     

Colonising the land requires advances in: mechanical support + respiratory gas exchange Bony skeleton (including that of the fins) provided the necessary mechanical support for 4limbed (tetrapod) locomotion Lungs provided the necessary respiratory apparatus. Colonisation of the land by Vertebrates A crude lung developed early on among bony fishes (to enable them to withstand low oxygen levels in water, through gulping of air) One lineage (which gave rise to the land vertebrates) continued to use it as a lung, while in other fish it was developed it into a swim bladder

Why Colonise Land?   

Plenty to eat on land at this time E.g. arachnids, myriapods, insects Plenty of ‘new’ niches to be occupied

Which bony fishes led to land tetrapods?     

Panderichthyids - most likely Marine fishes Had a flattened head + long tail + 4 lobed fins Lobed fins used for walking under water, not land Clambered onto land from salt marshes to ambush passing land arthropods?

Amphibians  

Tied to water for breeding: external fertilisation of eggs (unprotected) + permeable skin Limb loss in some amphibians – associated with burrowing & swimming (caecilians)

Reptiles   

Mesozoic: the Age of Reptiles (dinosaurs, pterosaurs, ichthyosaurs) Massive adaptive radiation of diverse forms An important extrinsic factor was the drier climate (bad for amphibians). • 3 intrinsic factors were: - Insemination / fertilisation became internal - Coupled with internal fertilisation was the development of the amnion: a membrane enclosing the embryo in liquid. Possessors of amniotic egg less dependent on aquatic habitats for reproduction. Shell protects amnion + embryo + yolk sac. Yolk sac enables development to a more advanced stage of development – improves progeny’s survival chances - Scaly skin (reduces evaporation from body)

Extrinsic factors that promoted reptile diversification 

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Global warming - Caused fragmentation of tropical rainforests - This resulted in isolation of populations – promoted speciation Climate-caused demise of amphibians - Released early forms of reptiles from competition (reptiles could cope with drier climate)

Limb Reduction  

Associated with (probably evolved due to) burrowing habit But advantageous in other circumstances (arboreal habit / swimming / movement through dense vegetation / movement over sand &c.)

Bird Evolution

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Archaeopteryx, the first known bird, discovered in the early 1860s In theropods, like the oviraptorosaurs, we find several new types of feathers One is branched and downy Others have evolved a central stalk, with unstructured branches coming off it and its base Archaeopteryx has a vane-like structure in which the barbs are well-organized and locked together by barbules This is identical to the feather structure of living birds Proto-wings possibly enabled lift: - Gliding during short duration, low altitude leaps during running - Perhaps assisted prey capture / escape from predators Flapping flight + hollow bones came later on in bird evolution

Modern Birds       

Different types ...