Continuity of Species ppt 3

What are forms of evidence used to support the theory of evolution?

Some forms include fossils, comparative anatomy, comparative genetics, embryology, comparative bio-chemistry.

What should evidence for evolution demonstrate?

Evidence for evolution should demonstrate increasing complexity of organisms, increasing variety of species, relatedness/common ancestry, decrease in unfit species.

What is the most important thing to remember about evolution?

The more similar organisms are to each other the more recent their common ancestor, as there has been less time for mutations, different selection pressures, genetic drift to make gene pools different.

What are fossils?

Fossils are the preserved evidence of organisms that once existed on earth, found in rocks or soils.

Example of fossils

Examples include the whole body of the organism, the bones or partial bones of the body, the tracks or footprints of the animal, and the faeces of the organism (coprolites).

How are fossils formed?

Fossils are often formed when an animal or plant dies by catastrophic events such as a flood. It needs rapid covering by sediments to stop the decomposing, weathering or scavenging processes.

What is the fossil record?

The fossil record is the variety and placement of fossils in the geological strata that is used as evidence by evolutionary scientists.

Why is the fossil record important?

The fossil record is important because it confirms Darwin’s style tree diagram that shows how various species have common ancestors. These common ancestors are called ‘transitional forms’.

How does the fossil record contradict the story of evolution?

It contradicts as the lack of transition fossils is of serious concern. It should be expected that there are more fossils showing organisms transitioning from one form to another.

What is comparative anatomy?

Comparative anatomy is when scientists compare the anatomy of several different organisms or species to see if there are similarities. If there are similarities, then they must belong to the same type or grouping of organisms. e.g. snakes and lizards both being reptiles

What are homologous structures?

Homologous structures are structures within different organisms which are similar in shape, but not necessarily function. The development of these structures is often controlled by similar genes within each organism. Similar genes and structure is due to common ancestry.

What are analogous structures?

Analogous structures are structures in different species that have similar functions, but are not due to common ancestry. e.g. sharks and dolphins share similar structures, they both have streamlined shape

What is embryology?

Embryology is the study of the embryos of multi-celled organisms. Similarities in structures during the stages of development is supposed to mean that there is a common link between the species. The longer in development they are similar the more closely related they are.

What is comparative bio-chemistry?

Comparative bio-chemistry is where scientists examine and compare the DNA base sequence of various organisms to see if there are any differences and similarities. Mitochondrial DNA is used rather than nuclear DNA due to its stability.

How does comparative bio-chemistry support the theory of evolution?

The more similarities in base sequence there are, the closer the relationship between the two organisms or species = recent speciation. Time would mean more mutations would accumulate and DNA would become increasingly different.

What is the purpose of DNA hybridisation?

The purpose of DNA hybridisation is that it gives a measure of ‘relatedness’ and can be calibrated as a molecular clock against known fossil dates.

What are the two types of fossil dating techniques?

The two types are relative dating and absolute dating.

What is relative dating?

Relative dating compares the ages of one fossil or rock with another to determine which is older. It requires that sedimentary rocks forms in layers and the fossils are the same age as the layer in which they are found. Index fossils and fluorine analysis are two methods of relative dating.

What are index fossils?

Index fossils are a type of fossil which can be used to compare the ages of strata in different locations, which is called stratigraphy. For a fossil to be considered an index fossil they must have been widespread in where it lived, lived in narrow period of time, have been abudant in numbers and easy to identify.

What is fluorine analysis?

Fluorine analysis is when you compare the amounts of fluorine in different bones found in the same rock. Fluorine is absorbed into the bones from the water in the surrounding rock layer. This happens at a slow rate, and also depends on the amount of fluorine in the water.

What is absolute dating?

Absolute dating is the methods that give the actual age of the rocks and fossils. These methods include radioactive dating and tree rings.

What is radioactive dating and how does it work?

Radioactive dating estimates the age of once-living organisms by measuring the decay of Carbon-14, a radioactive isotope. Living organisms maintain a constant ratio of C-14, but when they die, C-14 decays into nitrogen at a steady rate, allowing scientists to calculate time since death.

What assumptions does radioactive dating rely on?

It assumes the decay rate of C-14 is constant and that the amount of C-14 in living organisms has always been the same throughout history.

What is the method tree rings and how does it work?

Tree rings count the growth rings on a tree. The growth rings are laid down each year, leaving a visible line in the wood. A standardised scale is used to analyse different trees and their growth patterns. The problem is that you can only compare the growth rings of trees from the same area, and not other areas.

What are the 4 era’s in the geological timescale?

The precambrian era, the paleozoic era, the mesozoic era and the cenozoic era.

What were the main events in the precambrian era?

The precambrian era extends from 4.5 billion years ago to 540 million years ago. Early life formed in this era. These early forms were simple organisms that gradually evolved into more complex organisms like worms and jellyfish.

What were the main events in the paleozoic era?

The paleozoic era extends from 540 million years ago to 250 million years ago. During this era the marine organisms began to develop in complexity, plants and vertebrates colonise land. Late in the era, dinosaurs appear along with increasingly complex plant species.

What were the main events in the mesozoic era?

The mesozoic era extends from 250 million years ago to 65 million years ago. In this era, reptiles were the dominant animal species, but birds and mammals are fast appearing. Flowering plants evolve.

What were the main events in the cenozoic era?

The cenozoic era extends from 65 million years ago till now. Dinosaurs become extinct in this era, while flowering plants and mammals become more prevalent. Warmer climate develops and humans appear.