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47 Cards in this Set

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What are the conditions of Early Earth?

- Massive oceans existed

- No ozone layer

- No free oxygen in the air

- Lots of volcanic activity

- Violent electric storms common

- Atmosphere contained some water vapour, hydrogen, carbon dioxide, carbon monoxide, nitrogen, methane and ammonia

What is the relationship between the conditions of early Earth and the origin of organic molecules

- The elements needed to create the organic compounds were present in the atmosphere

- The lack of ozone layer, the frequent electric storms and the volcanic activity could have provided the energy for molecules to be formed

What does the existence of organic molecules in the cosmos (e.g. on meteorites) imply for the origin of life on Earth

The discovery of organic molecules on meteorites implies there are organic molecules in the cosmos.

This means early Earth may have been 'seeded' with these molecules from the cosmos and the first cells may have arrived from the cosmos

Name two scientific theories to the evolution of the chemicals of life

Spontaneous generation

Chemosynthetic theory

Outline the theory of Spontaneous generation

- Living things arise spontaneously from non-living matter

- Redi showed that maggots did not rise from rotten meat, but only when an adult fly visited the meat

- This disproved the theory

Outline the Chemosynthetic theory

- The early atmosphere of earth contained all necessary material to form chemical components for life

- Organic molecules could have been created in slow spontaneous reactions using energy from UV radiation or lightning

- These molecules slowly collected in the surface layers of the ocean to form an organic 'soup'

- These molecules then combined to form larger structures, and eventually cells

What did Oparin and Haldane suggest?

They suggested that the primitive atmoshpere was reducing (as opposed to oxygen rich), and if there was an appropriate supply of energy (e.g. lightning storms, UV), then a wide range of organic compounds might be synthesised

Describe the Urey-Miller experiment

- It tested the chemosynthetic theory

- Confirmation that several of the key molecules of life could have been synthesised on the primitive Earth in the kind of conditions that were envisaged by Oparain and Haldane

- The molecules could then have gone through prebiotic chemical processes, leading to the origin of life

How did Urey and Miller test the chemosynthetic theory?

By replicating the conditions envisaged by Oparin and Haldane and providing sufficient energy (like the UV and thunder storms) to from organic molecules.

What was the debate about the composition of the early atmosphere?

- It possibly may not have been a highly reducing atmosphere

- If there was free oxygen present, the organic molecules would have reacted with it an decomposed

Identify some changes in technology that have assisted in the development of an increased understanding of the origin of life and evolution of living things

- Engineering > deep sea exploration

- Nanotechnology > analysing material at a sub-molecular level

- Radiometric dating methods > determining the ages of rocks and fossils

- Geophysics and seismology > greater understanding of the history of the Earth's structure and processes involved in its formation

- Microscopy > new understanding of structures at molecular level

Reason for Urey-Miller experiment

To test the hypothesis of Oparin and Haldane

Result of the Urey-Miller experiment

After a week of electrical discharge and recycling steam through their apparatus, they analysed the condensed liquid and it was found to contain amino acids, the building blocks for proteins

Importance of the Urey-Miller experiment in illustrating the nature and practice of science

It showed that the hypothesis and theories are welcomed in science, but are only accepted when backed up with scientific proof , that is, experiments

Contribution of Urey-Miller experiment to hypotheses about the origin of life

- Results supported Oparin and Haldane's theory

- Proved complex molecules can be produced from basic chemical components or inorganic molecules

Identify the major stages in the evolution of living things

- Organic molecules: Formation of organic molecules from inorganic molecules

- Membranes: Formation of a boundary around cells

- Procaryotic heterotrophic cells: Unicells that used organic molecules as a food source. No membrane-bound organelles.

-Procaryotic autotrophic cells: Unicells that developed pigments that allowed them to make their own food using the sun. No membrane-bound organelles

- Eurcaryotic cells: Unicells with membrane-bound organelles (both auto and hetero)

- Colonial organisms: Cells form a colony of independent cells which can be held together by a gelatinous matrix

- Multicellular organisms: Cells group together to form tissues, organs and systems performing specialised functions

Describe paleontological evidence that suggests when life originated on Earth

The earliest fossils found are of two types:

1) Microfossils: similar to present-day single-celled anaerobic procaryotic organisms

2) Stromatolites: Layered clumps of photosynthetic procaryoitc cells called cyanobacteria

What are the three places that stromatolites and microfossils can be found?

- Warrawoona Group in Western Australia

- Fig Tree Group in South Africa

- Gunflint Chert rocks on the shores of Lake Superior in North America

Describe the geological evidence that suggests when life originated on Earth?

- The first primitive cells were heterotrophic

- They developed pigments that allowed them to photosynthesise

- A by-product of this was oxygen

- There was an explosion in the abundance of these organisms

- The oxygen they produced was at first taken by the rocks

- These oxidised, red banded rocks can bee seen today in red bedrock formations

Describe the formation of the ozone layer

- When all oxidisable surface rock was saturated with oxygen, oxygen began to build up in the atmosphere

- UV radiation from the sun began to react with the oxygen in the atmosphere to form ozone, until an ozone layer formed around the earth

What does the ozone layer do?

It acts as a shield, absorbing UV radiation so that less reaches the surface of the Earth

Explain the significance of the change from an anoxic to an oxic atmoshpere

- Anaerobic organisms declined

- As oxygen levels rose, photosynthetic organisms became more abundant

- The ozone layer protected living things from the harmful effects of UV rays

- This protection enabled living things to colonise the land

- As oxygen levels rose, living systems developed ways to use oxygen directly to produce chemical energy

- Aerobic organisms evolved directly to produce energy more efficiently by the process of respiration

- Greater metabolic activity became possible and organisms could be more active

- Increase in size and complexity of organisms

Discuss ways in which developments in scientific knowledge may conflict with the ideas about the origins of life developed by different cultures

- Different cultures have developed different ideas to try to explain the origins of life

- They are linked to the religious and spiritual beliefs of a culture

- The development of scientific knowledge about the origins of life may conflict with some of these ideas

Describe technological advances that have increased out knowledge of procaryotic organisms

- Light and electron microscope: greater resolution and magnification to determine internal structure of prokaryotes

- Submersible craft: investigation of life forms that live near hydrothermal vents

Describe the main feature of the environment of Archaea

- Anaerobic environments

- E.g. deep soils or bogs, digestive system of herbivores,

The role of Archaea in its environment

- Converts CO2 and H2 produced from fermentation into methane

- Releases methane into atmosphere, contributing to carbon cycle

- Plays a role in the final step of the decomposition or organic matter and the recycling of carbon

- Archaea in the digestive system of herbivores assist the break down of cellulose

Describe the main features of the environment of bacteria

- Warm temperature

- Water freely available

- Low in salt or other solutes

- Sunlight or organic compounds plentiful

- Oxygen not so important

The role of bacteria in its environment

- Evolve oxygen into the atmosphere

- Primary producers in the food chain (photosynthetic)

- Powerful fermentation capabilities

- Some replace oxygen with nitrate and sulphate

What is a classification system?

When biologists group together organisms that have similar characteristics.

Why do scientists classify organisms?

- To make the study of the enormous diversity of life easier

- To understand the relationship between organisms

- To talk to other biologists about organisms without having to describe organisms in detail

- To predict information

What is taxonomy?

The science of identifying, classifying and naming organisms

What is systematics?

The science of studying the relationships between organisms

List the three classification systems

- 6 kingdoms (most recent)

- 5 kingdoms

- 3 kingdoms

Describe the selection criteria of the 6 kingdom classification system

- Molecular criteria

- Order of bases in particular genes

The advantages and disadvantages of the 6 kingdom classification system?


- provides genetic similarities between organisms

- more information leading to possible evolutionary relationships between organisms

- Can infer when past evolutionary diversion from a common ancestor occurred


- Requires costly, time-consuming procedures

- Requires the use of experts in molecular techniques

- Differing interpretations of scientists

Describe the selection criteria of the 5 kingdom classification system

- Structural features

- Procaryotic or eucaryotic

Advantages and disadvantages of the 5 kingdom classification system


- Easily observed in an organism

- More constant in an organism's lifetime (non seasonal change or change in maturity)

- Can infer reproductive methods


- Structures may vary between males and females of a species

- Internal biochemistry (genetic similarities) is not available for inferring evolutionary links

Describe the selection criteria of the 3 kingdom classification system

- Structural features

- Organised body and life

- Power of locomotion

Advantages and disadvantages of 3 kingdom classification system


- Easily observed in an organism

- More constant in an organism's lifetime

- Can infer reproductive methods


- Structures may vary between males and females

- Internal biochemistry not available for inferring evolutionary links

Explain how levels of classification of organisation in a hierarchical system assist classification

- Having simple levels of hierarchy for classification makes it an easy and systematic way to name organisms according to their characteristics

The rank order of groups commonly used today is:

- Kingdom

- Phylum

- Class

- Order

- Family

- Genus

- Species

Why is the classification system continually revised?

Changes in technology are continually increasing our knowledge on organisms

Give examples of changes in technology that impact the development of revision of biological classification systems

- Light and electron microscopes: revealed more and more levels of detail of their internal structure

- Molecular biology and biochemistry: more information on evolutionary relationships between organisms. Closer analysis of differences at a molecular level

- Gene frequency studies and mitochondrial DNA studies: help create 'gene trees' to describe relationships between organisms

Describe the main features of the binomial system in naming organisms

An organism is given a name consisting of two words.

The first is the species within the genus (always with a capital letter).

The second is the genus.

Both words printed in italics

Definition of species

A group of organisms that can interbreed to produce fertile offspring .

Identify some difficulties experienced in classifying extinct organisms

- It is impossible to apply the definition of a species to extinct species

- Fossil evidence may be incomplete or not show enough detail to classify the organism

- It it has been long extinct, there may not be any living ancestor to compare it to

- The classification system allows scientists to name fossils even if they only have part of an organism. This means that an organism may end up with two names

How can the classification of organisms assist in developing an understanding of present and past life on Earth


- sense of order to a vast range of different types

- makes it easier to study

- Simplifies the description of living things

- One group can indicate several features


- Biologist around the world use the same system for naming

- Internationally accepted names

- Written in Latin

- Prevents confusion


- Classification is the first step to learning about the relationships of organisms to their environment

- Once the endangered species are identified, we take actin to conserve + protect them


- Assists in interpreting the diversity of life on Earth