History of ideas

Where did all the species come from? Special creation of species – each was individually created Transmutation of species – each species can change over time to produce new species Evolution – species can change and give rise to new forms – descent with modification

Explaining biodiversity De Maillet - species could originate instantaneously Erasmus Darwin – recognised that all warm-blooded animals originated from one living organism and had the ability to change and improve over time Jean Baptise Lamarck – individual organisms could respond to changes in their lifetime and pass these adaptations on to next generation Biodiversity = total variety of living things on Earth

Charles Darwin – Alfred Russel Wallace Theory of evolution by natural selection Presented 1858 & published Based on observations made on voyages to remote islands Noted very different species in Southern Hemisphere compared to Northern, even in similar habitats

Evidence of Evolution Fossil Record – bones, teeth, shells, leaves, footprints, casts, pollen grains Transitional fossils – demonstrate the transition from one species to another Comparative biochemistry – comparing genes and proteins Comparative anatomy – comparing structures, organs and embryos Bio-geographic distribution – examining diversity of species in different geographical areas Fossilisation = preservation of the remains of an organism long after death

Fossil Formation When organisms die, their remains may be compressed under layers of sediment With pressure, this sediment forms rock, trapping the remains and preserving them for long periods of time

Fossil Record Fossils are dated based on the type of rock that they are found in A record of fossils found is kept and aligned with the geological time- scale that related to the age of the Earth

Geological time-scale Estimated age of Earth 4500 million years ago (Mya, Ma, Myr) Based on studies of rock of relative ages Developed in 18 th and 19 th centuries Divided into intervals of time – eons, era, period, epoch

Ma = million years ago

Estimating Relative Rock Ages Principle of superposition – deepest rock is oldest Principle of correlation – based on identifying key fossils within the rock type that correlate to a particular period of time

Rock Layers

Problems with estimating relative age

Calculating Absolute Rock Ages Radiometric dating – with radioactive isotopes These are able to decompose by losing protons and neutrons to form a new element They have known a half-life Electron Spin Resonance – measures amount on energy in electrons of substance For substances 50, ,000 years old

Radioactive half-life Half life

Examples of Radioactive isotopes Radioactive Parent Isotope Stable Daughter Isotope Half-lifeUseful for Potassium -40 Argon-401,300,000,000 Dating igneous rock 500,000 years or older Rubidium- 87 Strontium ,000,000,000 The most ancient igneous rocks Uranium- 235 Lead ,000,000 Dating igneous rock ,000,000,000 years old Carbon-14Nitrogen-145,730 Dating organic matter up to 60,000 years old

Fossil Record This shows evolution of horses through natural selection - Hooves better suited to grass plains - Teeth better suited to eating grass

Transitional Fossils Transitional Modern whale Land mammal ancestor to modern whale

Comparative Anatomy Homologous features – similar structure evolved from common ancestor – may have different functions (eg pentadactyl limb) Analogous features – structures with similar functions but different evolutionary origins (eg. Wings) Vestigial organs – structure evolved from common ancestor but functionless (eg. Appendix in humans)

Homologous – pentadactyl limb Pentadactyl = five fingers All have same evolutionary origins but may have different functions

Analogous – the wing Bat wing Moth wing Bird wing

Comparative Embryology The very beginnings of embryology show many similarities The embryos diversify over the period of gestation Mammal embryos display gill slits during development – due to common ancestor?

Comparative biochemistry Proteins – amino acid sequence DNA hybridisation – mixing single strand of DNA from one species with single strand of another High or low complementarity determined by melting temp of hybrids Estimates ‘genetic distance’ Observe Chromosome banding patterns and chromosome ‘paint’ using karyotype techniques

Comparing DNA Hybridisation Comparing bands in chromosomes

Chromosome Paint