Unit F795 – the 2011 spec

A2 Unit F795: Evolution of Life, Earth & Climate
Module 1: Formation of fossils
5.1.1
Understand the different types of preservation of hard skeletal tissues

Candidates should be able to:
(a) describe how replacement of body fossils occurs and how fossils are altered from less stable aragonite to stable calcite;
(b) explain how silicification occurs, where wood or other organic materials are replaced by silica;
(c) explain how pyritisation occurs as a result of anaerobic bacterial action on the deep sea floor;
(d) explain how carbonisation of plant and graptolite fossils occurs as a result of loss of volatiles, due to increased pressure and temperature;
(e) describe how internal and external moulds and casts are formed.

5.1.2
Understand exceptional preservation of fossils

Candidates should be able to:
(a) explain how rapid burial, lack of oxygen, lack of scavengers, rapid deposition of fine sediment and early diagenesis affect the level of detail in the fossil record;
(b) explain why the fossil record is incomplete;
(c) describe how amber was formed from tree resin that trapped small organisms (especially insects) and then hardened;
(d) describe how tar pits trapped organisms;
(e) describe the preservation of a varied assemblage of organisms in the Burgess Shale;
(f) describe the preservation in the Solenhofen Limestone.

5.1.3
Know about trace fossils and understand their use in interpreting palaeoenvironments

Candidates should be able to:
(a) define trace fossils as a record of the activity and/or behaviour of an organism;
(b) describe how tracks (footprints) are formed and how trails are formed as impressions of whole animals at rest or travelling; explain how dinosaur footprints are used to interpret the size and locomotion of dinosaurs;
(c) explain how burrows (soft substrate) and borings (hard substrate) are structures for dwelling, protection or feeding;
(d) explain that a low energy environment is required to preserve tracks and trails and that burrows can be formed in variable energy environments.

5.1.4
Understand the use of fossil assemblages in interpreting palaeoenvironments

Candidates should be able to:
(a) define the terms: fossil life assemblages, fossil death assemblages and derived fossils;
(b) explain how fossil assemblages can be used to interpret palaeoenvironments;
(c) describe the methods used and difficulties encountered in inferring the mode of life of extinct fossil groups: trilobites, graptolites, ammonoids, dinosaurs.

Module 2: Morphology of fossils and adaptation of organisms to live in different environments
5.2.1
Know the morphology of trilobites and understand the adaptations for different environments

Candidates should be able to:
(a) describe the trilobite exoskeleton: cephalon, thorax, pygidium, glabella, compound eyes, facial suture, free cheek, fixed cheek, spines, pleura, nature and position of the legs and gills, and explain the inferred functions of these features;
(b) describe and explain adaptations for a nektonic life style, including eyes on stalks, small size, separated pleura and spines;
(c) describe and explain adaptations for a planktonic lifestyle including inflated glabella, small eyes or no eyes, few pleural segments and small size;
(d) describe and explain adaptations for a benthonic life style including ability to enrol, many thoracic segments and legs, 360o vision;
(e) describe and explain adaptations for an infaunal life style including, a large cephalic fringe, cephalic pits, extended genal spines and no eyes.

5.2.2
Know the morphology of tabulate, rugose and scleractinian corals; understand that fossil corals may indicate a tropical, marine, reef environment

Candidates should be able to:
(a) describe coral morphology; septa, tabulae, dissepiments, columella, calice and corallite within the corallum; describe solitary and compound forms;
(b) compare the morphological similarities and differences between tabulate, rugose and scleractinian corals;
(c) describe and explain the conditions that modern corals need for good growth; explain how modern corals have a symbiotic relationship with photosynthetic algae and that the conditions for growth were probably similar in the past;
(d) describe the modern distribution of coral reefs and explain how coral reefs are formed.

5.2.3
Know the morphology of brachiopods

Candidates should be able to:
(a) describe brachiopod morphology: symmetry, shape, pedicle and brachial valves, ornament, pedicle, foramen, adductor and diductor muscle scars, umbo, commisure, lophophore support system, pedicle and shape of hinge line, and where appropriate explain the functions of these features;
(b) explain how brachiopods feed as filter feeders using the lophophore;
(c) describe how ancient brachiopods lived in shallow, muddy or carbonate seas.

5.2.4
Know the morphological differences between regular and irregular echinoids that reflect their respective modes of life

Candidates should be able to:
(a) describe echinoid morphology: shape of test, symmetry, ambulacra, interambulacra, spines, tubercles, pore pairs for tube feet, position of periproct / anus, position of peristome / mouth, apical system, madreporite, labrum, fasciole, plastron, anterior groove and explain the functions of these features;
(b) describe an epifaunal (scavenger) mode of life for the regular echinoids;
(c) describe an infaunal (burrowing) mode of life for the irregular echinoids;
(d) compare the morphological similarities and differences between regular and irregular echinoids and explain how they reflect their respective modes of life.

5.2.5
Know the morphology of bivalves and understand how their adaptations for different environments

Candidates should be able to:
(a) describe bivalve morphology: symmetry, left and right valves, shell shape and gape, umbone, ornament, dentition, pallial line and sinus, adductor muscle scars and explain the functions of these features;
(b) describe and explain adaptations for cemented forms on hard substrate with thick shells to withstand a high energy environment;
(c) describe and explain adaptations for non-cemented, free-lying forms so they do not easily sink into soft substrate;
(d) describe and explain adaptations for byssally attached forms with rounded and elongate shells designed to withstand high energy on rocky shores;
(e) describe and explain adaptations for nektonic (swimming) forms with corrugated, thin shells;
(f) describe and explain adaptations for infaunal shallow and deep burrowers and compare these adaptations.
(g) compare the morphological similarities and differences between brachiopods and bivalves.

5.2.6
Recognise minor fossil groups and the environments in which they live

Candidates should be able to:
(a) describe and recognise gastropods using the shape of the coiled shell, spire, and body chamber; describe the mode of life of gastropods in high and low energy shallow seas;
(b) describe and recognise belemnites using the shape of guard and phragmacone; describe the mode of life and preservation of belemnites in marine conditions;
(c) describe and recognise crinoid morphology: calyx, brachia, stem and ossicles; explain how crinoids may be disarticulated after death and form bioclastic limestone; describe the mode of life of ancient crinoids in shallow carbonate seas.

5.2.7
Know about the main microfossil groups and understand their use in stratigraphy

Candidates should be able to:
(a) describe the composition of ostracods, foraminifera, conodonts and radiolaria and the environments in which they lived;
(b) state that most fossil spores and pollen are derived from vascular land plants;
(c) outline the main uses of microfossils in stratigraphy.

Module 3: Fossil evidence of the evolution of organisms and mass extinctions
5.3.1
Know the meaning of evolution

Candidates should be able to:
(a) explain the Darwinian theory of evolution; state that adaptations are a result of evolution.

5.3.2
Know the morphology of graptoloids (graptolites) and the morphological changes that show the evolution of graptolites in the Lower Palaeozoic

Candidates should be able to:
(a) describe graptolite morphology: stipe, sicula, thecae, rhabdosome and nema;
(b) describe the changes in morphology as graptolites evolved through the Lower Palaeozoic:
(i) describe the change in the number of stipes in the rhabdosome;
(ii) describe the change in the attitude of the stipes (pendent, horizontal, reclined, scandent);
(iii) describe the changes in the shapes of the thecae (simple, hooked, sigmoidal);
(iv) describe the change in the shape of the rhabdosome (uniserial, biserial);
(c) deduce the probable mode of life of graptolites as planktonic colonial filter feeders within the water column.

5.3.3
Know the morphology of nautiloids and ammonoids and the morphological changes and evolution of nautiloids and ammonoids in the Palaeozoic and Mesozoic

Candidates should be able to:
(a) describe nautiloid and ammonoid morphology: shell shape, form of coiling, ornament, aperture, body chamber, suture lines, saddles and lobes, siphuncle, septal necks, septa, keel, sulcus, umbilicus and where appropriate explain the inferred functions of these features;
(b) describe the changes in morphology as nautiloids and ammonoids evolved through the Palaeozoic and Mesozoic:
(i) describe the changes in suture lines from simple orthoceratitic to goniatitic (Carboniferous), ceratitic (Triassic) to complex ammonitic (Jurassic and Cretaceous);
(ii) describe the changes in the position of the siphuncle and the septal necks between nautiloids and ammonoids;
(iii) describe the changes in shape of the shell from involute to evolute and increases in ornamentation;
(c) explain that heteromorphs are either evolutionary changes or adaptations to different environments;
(d) deduce the probable mode of life of ammonoids as nektonic.

5.3.4
Know about the evolution of amphibians from fish

Candidates should be able to:
(a) describe the similarities between coelacanths and lungfish and the early amphibians in the Devonian using skull morphology, fin bones, limb bones, teeth, body shape, tail fin and scales;
(b) explain how early amphibians were adapted to terrestrial life in the Carboniferous.

5.3.5
Know about the evolution of dinosaurs

Candidates should be able to:
(a) explain the advantages of amniotic eggs for life on land;
(b) describe how dinosaurs evolved into the Saurischia (saurapoda, therapoda) and Ornithischia;
(c) describe the characteristics of saurischian dinosaurs: arrangement of hip bones, grasping hand, asymmetrical fingers, long mobile neck;
(d) explain how Diplodocus (sauropod herbivore) and Tyrannosaurus (therapod carnivore) are adapted to different modes of life;
(e) describe the characteristics of ornithischian dinosaurs: arrangement of hip bones, armoured, horned and duck billed;
(f) explain how Iguanodon was adapted to its mode of life on land: horny beak, teeth, hinged upper jaw, defensive spike, hand adaptation, quadrupedal and bipedal stance;
(g) describe how the birds evolved from therapod dinosaurs;
(h) describe the similarities of Archaeopteryx to both dinosaurs and birds.

5.3.6
Know about the major mass extinction events

Candidates should be able to:
(a) define the term mass extinction and state that there have been a number of mass extinction events over geological time;
(b) describe and explain the possible reasons for the mass extinction at the Permo–Triassic boundary; explain how the evidence for major volcanic activity (Siberian Traps) can be used to account for this mass extinction;
(c) describe and explain the possible reasons for the mass extinction at the Cretaceous–Tertiary boundary; explain how the evidence for a major asteroid impact and volcanic activity (Deccan Traps) can be used to account for this mass extinction;
(d) state the fossil groups that became extinct at these boundaries.

Module 4: Dating methods, correlation and interpretation of geological maps
5.4.1
Know about radiometric dating

Candidates should be able to:
(a) explain how radiometric dating is used to establish an absolute timescale;
(b) describe and explain the limitations of radiometric dating based on the scarcity of appropriate radioactive minerals;
(c) describe and explain the problems of obtaining accurate radiometric dates, particularly with respect to sedimentary and metamorphic rocks;
(d) describe potassium-argon and rubidium-strontium methods of radiometric dating and explain how they are used to date different rocks of varied ages;
(e) plot and interpret half-life curves for these methods.

5.4.2
Know about relative dating

Candidates should be able to:
(a) describe and explain the use of superposition, original horizontality, way-up criteria, cross-cutting relationships, included fragments, unconformities and fossils to date rocks at the surface and in boreholes;
(b) describe and explain the problems of using relative dating when derived fossils and erosion may give contradictory evidence;
(c) explain how both relative and radiometric dating are used to create the geological timescale.

5.4.3
Use dating evidence to interpret geological maps

Candidates should be able to:
(a) recognise the age relationships between structures on simplified geological maps, cross-sections and photographs using both relative and absolute dates, correlation and zone fossils;
(b) describe the age relationships of beds using cross-cutting features: beds, faults, folds, unconformities and igneous features to interpret map and cross-section geological histories.

5.4.4
Know and understand the geological column

Candidates should be able to:
(a) outline early attempts made to estimate the Earth’s absolute age: salts in the ocean, rates of sedimentation, rate of cooling;
(b) describe the division of the geological column into eras and systems using both relative and absolute dating methods.

5.4.5
Know how rocks can be correlated

Candidates should be able to:
(a) describe and apply biostratigraphic correlation using first appearance, stratigraphic range, extinction and fossil assemblages; explain the problems of derived fossils or scarcity of fossils;
(b) describe and apply lithostratigraphic correlation using sequences of beds, thickness and composition; explain the problems of lateral variation and diachronous rocks;
(c) describe and apply chronostratigraphic correlation using tuffs and varves.

5.4.6
Know the main appearances and extinctions of key fossil groups and their use as zone fossils

Candidates should be able to:
(a) describe and explain the use of the first appearance and extinction of the main invertebrate fossil groups to establish a relative timescale for the Phanerozoic into eras and systems;
(b) state the stratigraphic ranges of trilobites, graptolites, tabulate, rugose and scleractinian corals, goniatites, ceratites and ammonites, regular and irregular echinoids, long hinged and short hinged brachiopods;
(c) describe and explain the factors that make a good zone fossil; outline the advantages and disadvantages of using graptolites, ammonoids and microfossils as zone fossils.

Module 5: Changing climate
5.5.1
Know that climate has changed over geological time

Candidates should be able to:
(a) define the term climate; describe changing climate in terms of icehouse – greenhouse cycles throughout geological time and explain the possible link to mass extinction events;
(b) describe how Milankovitch cycles may explain patterns of sedimentation, particularly in the Jurassic;
(c) describe the use of oxygen (18O and 16O) isotopes to determine water temperature;
(d) describe the use of carbon (13C and 12C) isotopes in identifying geological changes.

5.5.2
Know that there have been major changes in sea level over geological time

Candidates should be able to:
(a) interpret Vail sea level curves showing changes over geological time in comparison with modern sea level;
(b) explain how both isostatic and eustatic sea level changes take place;
(c) explain the relationship between sea level and climate change and the possible link to mass extinction events.

5.5.3
Know about the evidence for palaeoclimatic changes

Candidates should be able to:
(a) describe and explain the fossil evidence for palaeoclimatic changes: corals and plants;
(b) describe and explain the lithological evidence for palaeoclimatic changes: coal, desert sandstone, evaporites, boulder clay (tillite) and reef limestone;
(c) describe the evidence for the northward movement of the British Isles throughout geological time.

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