Evolution Flashcards
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algae
A group of organisms that photosynthesise but lack the complex range of cell types and organs found in land plants. Most algae are aquatic. All have chloroplasts.
amber
definition
Hardened tree resin.
antibiotic
definition
Substance that controls the spread of bacteria in the body by killing them or stopping them reproducing
bacteria
definition
Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium.
binomial
definition
Having two parts to a name. In the binomial system of classification, each organism is named for its genus then its species.
evolution
definition
The change of inherited characteristics within a population over time through natural selection, which may result in the formation of a new species.
fungi
definition
Non-green plants that obtain their energy by decomposing dead organic remains.
lichen
definition
A type of fungus that grows on rock.
mutation
definition
A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes.
natural selection
definition
The natural process whereby the best-adapted individuals survive longer, have more offspring and thereby spread their characteristics. Sometimes referred to as ‘survival of the fittest’
pathogen
definition
Microorganism that causes disease
phylum
definition
A taxonomic rank between kingdom and class (the plural is phyla). The arthropods, for example, are a phylum.
sediment
definition
Small fragments of rock and soilthat form layers.
species
definition
A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully.
tar
definition
Sticky substance found in tobacco smoke, which can cause cancer.
Darwin proposed that:
- individual organisms within a particular species show a wide range of variation for a characteristic
- individuals with characteristics most suited to the environment are more likely to survive and to breed successfully
- the characteristics that have enabled these individuals to survive are then passed on to the next generation
This theory is called natural selection.
Antibiotic resistance
Evidence for evolution - Resistant bacteria
Bacteria can evolve quickly because they reproduce at a fast rate. Mutations of bacteria produce new strains. Some bacteria might become resistant to certain antibiotics, such as penicillin, and cannot be destroyed by the antibiotic. The evolution of the bacteria is an example of natural selection and supports Darwin’s theory of evolution.
Development of resistance
The main steps in the development of resistance are:
(Evidence for evolution - Resistant bacteria)
1) random mutation occur in the genes of individual bacterial cells
2) some mutations protect the bacterial cell from the effects of the antibiotic
3) bacteria without the mutation die or cannot reproduce when the antibiotic is present
MRSA
Evidence for evolution - Resistant bacteria
The number of resistant strains has increased, partly due to the overuse and misuse ofantibiotics. This has resulted in more infections that are difficult to control.
MRSA is methicillin-resistant staphylococcus aureus, and it is very dangerous because it is resistant to most antibiotics.
MRSA
In order to reduce the rate of development of antibiotic resistant strains:
(Evidence for evolution - Resistant bacteria)
- doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections
- patients should always complete the full course of antibiotics to ensure all bacteria are killed and none survive to mutate and form resistant strains
- the agricultural use of antibiotics should be restricted
Antibiotic resistant bacteria
overview
Penicillin was the first antibiotic to be produced on a mass scale in the 1940s. It is derived from the Penicillium fungus, shown here growing on an agar plate.
Many new types of antibiotics were discovered during the 1950s and 1960s, but more recently, this has slowed greatly.
Recent concerns of increasing resistance have created the need for new antibiotics, but they are costly and very slow to develop. Some scientists fear that we are fighting a losing battle against resistant bacteria, which may ultimately lead to people dying from simple infections, for example following operations.
Evidence of evolution - Rock fossils
A fossil is the preserved remains of a dead organism from millions of years ago. Fossils are found in rocks and can be formed from:
- hard body parts, such as bones and shells, which do not decay easily or are replaced by minerals as they decay
- parts of organisms that have not decayed because one or more of the conditions needed for decay are absent for example, dead animals and plants can be preserved in amber, peat bogs, tar pits or in ice
- preserved traces of organisms, such as footprints, burrows and rootlet traces - these become covered by layers of sediment, which eventually become rock
Evidence of evolution - Rock fossils
The fossil record
Fossil remains have been found in rocks of all ages. Fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms in the newest rocks. This supports Darwin’s theory of evolution, which states that simple life forms gradually evolved into more complex ones.
Evidence for early forms of life comes from fossils. By studying fossils, scientists can learn how much (or how little) organisms have changed as life developed on Earth.
There are gaps in the fossil record because many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were may have been destroyed by geological activity. This is why scientists cannot be certain about how life began.
Tools as evidence for human evolution
Tools also provide evidence for human evolution. Primitive tools (flint hand axes) have been found in remains from the Palaeolithic Age (10,000 to 2.5 million years ago). More advanced tools (arrowheads) have been found from the Mesolithic Age (6,000 to 10,000 years ago), and even more advanced tools have been found from the Neolithic Age (4,000 to 6,000 years ago).
These dates are only approximate, as the tools have been dated from the environments they were found in. This is often the layers of sediment surround the tool. Dating can be done by radiocarbon dating or other techniques which look at the amounts of elements like iron or potassium. It is the assumed that the tool is approximately as old as the rock which surrounds it.
The pentadactyl limb
Many vertebrates have a very similar bone structure despite their limbs looking very different on the outside. This structure is known as the pentadactyl (five fingered) limb. This suggests that many vertebrates descended from the same common ancestor.
Although the limbs of crocodiles, birds, whales, horses, bats and humans all look very different they share the same five fingered bone structure. This provides evidence for the theory of evolution.
The pentadactyl limb
horses
The pentadactyl limb seen in the horse provides an excellent example of how evolution has happened. As the marshy ground became drier, horses with smaller feet were generally faster. They had an evolutionary advantage because they were able to avoid predators. Over many, many generations horse’s feet have evolved to be smaller and the horses themselves taller and stronger.
Linnaean system of classification
overview
Living organisms are classified into groups depending on their structure and characteristics. This system was developed in the eighteenth century by Carl Linnaeus. The classification of species allows the subdivision of living organisms into smaller and more specialised groups.
Kingdoms
Linnaean system of classification
The first division of living things in the classification system is to put them into one of five kingdoms. The five kingdoms are:
- animals (all multicellular animals)
- plants (all green plants)
- fungi (moulds, mushrooms, yeast)
- protists (amoeba, chlorella and plasmodium)
- prokaryotes (bacteria, blue-green algae)
Linnaean system of classification
Living things can then be ranked according to:
(least to most specific)
- Kingdom
- phylum
- class
- order
- family
- genus
- species
(Linnaean system of classification)
Phylum follows Kingdom and has many different organisms, including three examples from the Animal Kingdom:
- chordata, which have backbones
- arthropod, which have jointed legs and an exoskeleton
- annelids, which are segmented worms
(Linnaean system of classification)
Class is an additional sub-division, which for example, results in the Chordata phylum being divided into:
- mammals
- birds
- amphibians
- fish
- reptiles
(Linnaean system of classification) Order follows class and as an example, mammals can be further sub-divided into a variety of different groups such as:
- carnivores
- primates
(Linnaean system of classification)
Orders are broken down into families. Here are a few examples of which carnivores can be divided into:
- canidae - dogs
- felidae - cats
(Linnaean system of classification)
Genus, the Felidae family can be further sub-divided into four genus examples:
- acinonyx - cheetah
- panthera - lion and tiger
- neofelis - clouded leopard
- felis - domestic cats
(Linnaean system of classification)
Species is the final classification stage, and the genus panthera can be divided into:
- panthera leo (lion)
- panthera tigris (tiger)
(Linnaean system of classification)
As an example, the complete breakdown of the classification of lions:
- kingdom - animal
- phylum - vertebrate
- class - mammal
- order - carnivorous
- family - felidae
- genus - panthera
- species - panthera leo
Mnemonic to remember order of classification of living organisms.
Kids prefer candy over fresh green salad
Impact of modern developments of classifying systems
Technology associated with biology has advanced throughout the years, which has allowed the current classification system to be enhanced by using genetic analysis of DNA sequences.
Originally Linnaeus’ system relied purely on human judgement in order to compare the characteristics of various organisms. Now the comparisons of DNA sequences have allowed the relationship of organisms to be explored further. In some cases, species that are more closely related may have fewer differences contained within the DNA sequences. DNA sequences are shown as the order of DNA bases, abbreviated as A, C, G and T.
There has been debate in history over the classification of the red panda and the giant panda. Some argued that they should belong to the bear family and others argued that they are more like racoons. Following the development of DNA sequencing technology, it has been shown that the red panda and ginat panda are not very closley related genetically. DNA analysis showed the giant panda to be a bear, and the red panda to be more closely related to a racoon.
Impact of modern developments of classifying systems
Three-domain system
Classification systems have continued to be developed by other scientists, such as Carl Woese who developed the three-domain system. This is based on evidence genetic analysis.
Genes of an organism code for proteins. It has been demonstrated that some organisms have parts of their genes that are not used in making proteins and other organisms that use entire genes to code for proteins, with no unused portions. This information has informed the three-domain system.
Impact of modern developments of classifying systems
Three-domain system
The system divides organisms into:
- Archaea (primitive bacteria):
These cells usually live in extreme environments. They have no nucleus and have unused sections of genes. - Bacteria (true bacteria):
Bacteria cells have no nucleus and no unused sections of genes. - Eukaryota (including protists, fungi, plants and animals):
These have a nucleus and have unused sections of genes.
What is Archaea?
Archaea (primitive bacteria):
These cells usually live in extreme environments. They have no nucleus and have unused sections of genes.
What is Bacteria?
Bacteria (true bacteria):
Bacteria cells have no nucleus and no unused sections of genes.
What is Eukaryrota?
Eukaryota (including protists, fungi, plants and animals):
These have a nucleus and have unused sections of genes.
Examples of bacteria.
- Cyanobacteria
- Heterotrophic bacteria
Examples of archaea.
- Halophiles
- Thermophiles
Examples of eukaryota.
- Animals
- Fungi
- Plants
- Chromists
- Alveolates
- Rhodophytes
- Flagellates
- Basal protists
Why can bacteria evolve more quickly than other species?
Bacteria can evolve more quickly because they reproduce quickly.
