There are more than 8 million species on the planet and with such large numbers, there is a need to accurately identify them in a way that is universal for scientists across the world to understand. The scientific process of classifying organisms (both living and extinct) is known as taxonomy. In the past, basic processes of identifying species were used but as scientific knowledge and technology has developed this system has been adapted. The modern classification system is much more accurate and sophisticated. This assignment will take a look at the classification systems and discuss evolutionary contributors. It will explain how domains are differentiated and additionally, will draw comparisons between species and describe adaptations which affect their categorisations.
1.2 Discuss historical taxonomy and evolutionary contributors
The history of classification started with the Greeks. Aristotle (384 BC-322 BC) was the first known philosopher to have attempted to group organisms based on shared characteristics. He divided organisms into plants and animals and then grouped them further using their unique features. This included if they live in water or on land, if they give birth to live young or eggs and animals with and without blood (now known as vertebrates and invertebrates). Aristotle’s student ‘Theophrastus’ (c. 371–c. 287 BC) developed his work further by writing the classification of plants.
It was not until the end of the 16th Century when there were enough innovations made to replace the works of the early Greeks. At this time, more explorations were made where different plant and animals were discovered and the development of the optic lens meant that species could be looked at in greater detail. This gained the attention of scientists who were able to examine organisms, before naming and sorting them, into any existing systems. The modern classification system started in the 18th Century with Carl Linneaus.
Systems for classifying organisms continue to change as new discoveries are made and technologies develop. The original systems only identified two kingdoms (plant and animal) but the current ‘Three Domain System’ is the most advanced system to date.
The levels of the modern classification system are as follows:
1.1 Explain biological classifications characteristics
Domain
In 1990 scientific advancements meant that organisms could be analysed at a molecular level. Carl Woese created the three domain system which is based on differences in the cell’s structure and genetic sequencing. Under this system, organisms are classified into the following domains:
• Archaea
• Bacteria
• Eukarya
Kingdom
1.3 Explain species grouping and relevance of genetic evolution
At first Linneaus divided all living organisms into just two kingdoms – animals and plants. But it is now acknowledged by scientists that there are five kingdoms. ‘They are split into their groups based on similarities such as how they obtain their food, the types of cells that make up their body and the number of cells they contain’. (Softschools.com, 2019)
The Five Kingdoms are as follows:
• Animalia
• Plantae
• Fungi
• Protista
• Monera
Phylum
Phylum is the next level of classification and is made up of 35 recognised Phyla. Phyla is used as way of grouping organisms based on shared physical similarities.
Examples include:
Arthropods: Have several pairs of jointed legs and a hard exoskeleton such as crustaceans, insects and arachnids.
Molluscs: Have soft bodies covered by a hard shell, such as snails.
Chordates: Have backbones. Examples include mammals, reptiles and birds.
Class
The phylum group then divides into smaller groups, known as classes. Each class shares even more characteristics e.g. birds share the similarity that they are covered with feathers and mammals are warm blooded.
Order
Classes split into further groups, known as orders. These organisms share even more characteristics. For example the Class Mammalia includes carnivores and primates, amongst others.
Family
Orders are divided into families of animals which share similar physical features. This is an important sequence as it starts to narrow the groups down. For example it includes Carnivora that can be divided into Felidae (cats) and Canidae (dogs).
Genus
1.3 Explain species grouping and relevance of genetic evolution
Genus follows on from Family and comprises of species who are closely related and have similar characteristics (e.g. appearance and behaviour) but are usually unable to breed with one another. For example, Felidae (cat) includes domestic and big cats who are categorised under different genus.
Species
Species is the lowest but most specific level of classification. A species can be defined as a group of organisms that are able to produce fertile offspring. Each species is named in Latin and in a way that reflects its features and characteristics. The name consists of two parts, its genus and then its species. This standardised format helps scientists across the world identify individual species.
2.2. Differentiate between reptiles and mammals
2.3 Relate to domain and classification categorization
2.4 Identify genetic processes of subcategorization and provision of examples of physical and genetic characteristics
All animals are classified into the Eukarya Domain and both mammals and reptiles form part of the Phyla group – Chordata. Within this classification they share many similar traits:
• Both are vertebrates, meaning that they have a backbone to protect a nerve cord that runs down the length of their bodies
• They breathe air and most live on land
• They have complex internal skeletons
• Most have paired limbs or fins
• They have similar internal body parts including muscular hearts with three or four chambers
• They reproduce sexually and use internal fertilisation
The table below highlights some of the key differences between Mammals and Reptiles:
Mammals Reptiles
Classification Kingdom Animalia
Phylum Chordata
Class Mammalia Kingdom Animalia
Phylum Chordata
Class Reptilia
Characteristics of class Mammals fit the Mammalia class because:
They are vertebrates
Are warm blooded
Mammals have fur or hair covering their bodies
They give birth to live young and have mammary glands to produce milk Reptiles fit the Reptilia class because:
They are vertebrates
They are cold blooded
Reptiles have scales covering their whole body epidermis
Reptiles lay eggs and have no mammary glands
Body regulation Endothermic – Mammals can maintain their own body temperature to keep warm.
Adaptations include:
Hair or fur to protect against cold weather
Ability to shiver
Some marine mammals have a layer of blubber to keep warm in cold climates
Shed fur during hot months
Pant or sweat to lose heat Exothermic – Reptiles are unable to maintain their body temperature and require an external source to keep warm.
Adaptations include:
Adopting certain body positions to maximise their exposure to the heat
Seek shade / cooler places when they need to cool down.
Scales help to prevent water loss and are tough enough to help prevent injuries.
Internal
Circulatory system Are warm blooded and have a heart with four chambers (left atrium, right atrium, left ventricle and right ventricle) to pump blood around the body and deliver nutrients. Their circulatory system helps to remove carbon dioxide and waste by-products of respiration. Most reptiles have a circulatory system designed to manage long periods basking in the sun and rapid bursts of energy. Their hearts have three chambers (left auricle, right auricle and ventricle) which controls the flow and separates oxygenated and deoxygenated blood. There are some exceptions (such as crocodiles) who have four chambers like mammals.
(Foundation,19)
Respiratory system
Most mammals live on land and get their oxygen from the air. Their respiratory system is made up of a system of muscles and airways that bring air into the lungs where oxygen is exchanged in blood for carbon dioxide. Only mammals have a diaphragm which helps to inflate and deflate the lungs. All reptiles breathe using lungs as they are adapted to life on land.
‘Lizards and snakes use muscles of the chest wall for this purpose. Crocodiles and alligators have a diaphragm similar to mammals that controls their breathing.’ (Foundation, 2019)
Brain Mammals have larger brains and are known to have a higher level of cognitive ability
Reptiles have smaller brains and lower levels of cognitive ability
Teeth Specialized teeth e.g. canines for ripping meat. Have only two sets of teeth during life time. Reptiles have teeth that replace often over a lifetime
Skull Single jaw bone, attached to the skull Jaw made up of multiple bones
Ears Three middle ear bones – mammals have very developed hearing Have a single middle ear bone
Glands Mammals have sweat glands
Mammary glands to feed their young Reptiles do not have sweat glands
Reptiles do not have mammary glands
Reproduction and offspring Mammals develop a placenta and give birth to live young
Offspring are dependant and mother produces milk to feed them Most reptiles lay eggs and lack a placenta
Most offspring are abandoned soon after they hatch
Even though Mammals and Reptiles make up two of the five vertebrate categories there are many differences that contribute to their classification. One of the main differences is the way they regulate body heat. Mammals are warm blooded and can regulate their own body heat whereas reptiles are cold blooded and need an external source to maintain their body temperature. Their circulatory and respiratory systems are adapted to manage their different lifestyles and habits. Some mammals live in water. Mammals give birth to live young, feed them milk from mammary glands and have dependant offspring. In comparison, most reptiles lay eggs, abandon their young and do not have mammary glands. Their appearances are very different too, mammals have fur or hair whereas reptiles have scales covering their bodies.
Explain the sub categorisation systems and describe how domains are differentiated, with extensive examples
All living things are categorised into three domains before being placed into more specific species groupings. Below highlights how domains are differentiated and the key points of species in each domain:
4.1 Identify multiple species in each domain
• Archaea
Archaea are organisms that have adapted to live in some of the most extreme habitats such as thermal springs, salt lakes and wetlands. They consist of microscopic single celled organisms with cells that lack a nucleus.
Some examples of Archaea include:
Halophiles: Adapted to living in very salty conditions and their cells are designed to prevent them from losing too much water. As such, they are able to cope with high concentrations of salt which other organisms would be unable to live in (as it would cause dehydration).
Methanogens: Produce methane as a by-product of metabolism and can be found in the digestive systems of some animals.
Thermophiles: Have membranes with an adapted structure to help them tolerate high heat. They can normally be found in hot or acidic conditions such as hot springs.
• Bacteria
Some defining features of Bacteria are:
• They are unicellular
• Have a cell wall
• No nucleus
• Are Prokaryotic (very simple cell)
Archaea and Bacteria are categorised differently because Archaea are genetically more similar to Eukarya than Bacteria are. Bacteria are extremely diverse and split into many categories. Some bacteria are harmless whilst others can cause disease. Examples include:
Chlamydia are parasitic and reproduce inside their host’s cells
E. Coli is found in the intestines and aid digestion. However, they can be harmful if they contaminate water or food and are then ingested
Enterococcus Faecium is a good bacteria which helps to maintain a healthy gut function
• Eukarya
4.2 Compare physical and genetic characteristics
Some of the defining characteristics of the Eukarya domain is that they have a true nucleus and have different cell walls from Bacteria and Archaeans. They have a unique method of cell division meaning that they can reproduce via asexual or sexual reproduction.
Examples include:
Fungi: Unicellular or multicellular organisms with eukaryotic cells. They do not make their own food and obtain nutrients through absorption. They have no root or stem and can be parasitic.
Plants: Multicellular organisms with unique cells containing chlorophyll. Chlorophyll helps plants to absorb light energy, water and carbon dioxide for creating their own food via photosynthesis.
Animals: Multicellular organisms capable of movement and obtain nutrients primarily by ingestion of other organisms. They have membrane bound organelles, lack cell walls and have a true nucleus holding genetic information in the form of chromosomes. Each chromosome contains DNA which is a two-stranded molecule held together by hydrogen bonds and is referred to a double helix due to its shape. DNA is an information carrying molecule and carries the instructions the organism needs for growing, developing, living and reproducing. Examples include insects and vertebrates.
Draw comparisons between species and describe complex adaptations which affect their categorisation; comment on the influences of physical and genetic characteristics and also external and/or environmental contributing factors
4.3 Describe adaptations within species and domains which influence classification
Differences can be seen between species which is normally a result of genetic or environmental variation or a combination of both. These influences result in unique adaptations which can help a species survive in the environment that they live in. Adaptations in organisms can either be seen as structural, physiological or behavioural.
Penguins live in extremely cold climates where there is a need to minimise heat loss. Penguins are classified in the order – Sphenisciformes which means that they are bird that stands upright, have webbed feet and wings designed like propellers for swimming underwater. Penguins have a layer of fat to maintain body temperature and a preen gland which coats their feathers in a waterproof oil. These structures mean that Penguins are well adapted to their environment. An example of a behavioural adaptation can be seen during snow storms when Penguins huddle together to maintain body temperature. Penguins have become un-territorial which allows them to work together to take it in turns to move from the outside of the huddle. Penguins have the ability to fast for several days and males have the unique ability to produce food from their oesophagus to feed their chicks.
Adaptations to environment can be seen in species living in hot climates. For example, Fennec Foxes live in the desert. They are well adapted as they are able to go for long periods without water and do not have sweat glands which prevents against excessive water loss. They have fur feet to protect from the hot sand and sandy coloured fur for camouflage. Big ears allow heat to escape and short fur which can shed if they are too hot. A behavioural adaption is that they are nocturnal which means that they avoid the hottest parts of the day.
In conclusion, classification has provided a standardised format of naming, grouping and identifying species for scientists across the world. It uses a system of grouping organisms and animals via a sequence of biological classification ranking order from domain to species. All organisms are named using a genus and species and this conveys information about its closest relatives. Biological characteristics affect how organisms are classified and many factors affect this including adaptations, systems, structures and functions. The classification system was based on a historic one but is continually updated and reviewed as scientific knowledge and technology advances.
Task 2
Conduct a web based search in order to:
Identify current classification processes, and the incorporation or new species and extinct species
Draw comparisons between classification and discuss the influence of demography when presenting your arguments
Comment on the ease of resource identification, and the availability and accessibility of information in your sources.
This task will identify modern classification processes and discuss how they are used to incorporate and identify new or extinct species. It will gather information about classification theories from a web based search and use this information to compare theories. Additionally it will comment on the ease of resources.
The modern classification system was developed by Carl Linnaeus in the 18th Century, who grouped and named organisms based on their observable, shared physical characteristics. It was a basic process, relying on human judgement to group those who looked most alike together into a category. Linnaeus’ original ideas are still accepted today but development of the microscope and advances in biochemistry meant that cells could be examined in much more detail. It is now known that species are not only linked by physical appearance but can also be compared at molecular level. The use of DNA has developed the process of classification and helped scientists to understand how closely species are related and how they may have evolved from one another. It is accepted that new species have evolved from existing species and that they share features based evolutionary descent. Each species has a unique sequence of bases in its DNA which allows scientists to identify and distinguish them from others. For example, species who are most closely related will have less differences in their DNA Sequences. This helps scientists to accurately identify new or extinct species and use the classification sequences to incorporate them into the system.
The 18th Century saw evolutionary theories develop. Darwin was an English Naturalist who was well travelled. He observed species in the Galapagos Islands which lead to his proposal that evolution was made via natural selection.
Key points of this theory are highlighted below:
Variation Different species show a range of variation which is a result of the genes they have inherited.
Inheritance of characteristics When a species has characteristics suited to the environment they are able to survive successfully and go on to adulthood. This gives more opportunity for them to reproduce and pass the advantageous genes on to their offspring. This results in more of their genes across the species and enables the species to evolve over time.
Time Over time individuals who are not as well adapted are less likely to survive or reproduce. This results in less of their genes across the species and can lead to extinction
(Beckett and Gallagher, 2001)
Charles Darwin’s theory has influence on the modern classification system because he proved that evolution of life can occur and that natural selection is the way in which these changes occur. Darwin’s theory was generally accepted and classification groupings started to reflect his explanation that all species have common ancestors. (Www2.palomar.edu, 2019) Current DNA sequencing backs up Darwin’s theory.
Alfred Russell Wallace was an explorer and naturalist who helped to develop the theory of natural selection. He proposed that “Useful variations will tend to increase, unuseful or hurtful variations to diminish” (Sciencenetlinks.com, 2019). Wallace’s theory was similar to that of Darwin’s as they both suggested that species have common ancestors. Their theories suggested that a species is able to survive successfully if they have advantageous qualities that allow them to do so. This gives them more opportunity to reach adulthood and pass their advantageous genes on to their offspring, resulting in more of the advantageous qualities amongst the species over generations.
John Baptiste Lamarck was a French biologist who suggested an alternative evolutionary theory to Darwin and Wallace. The key points are detailed below:
Characteristics An organ which is used frequently by an organism becomes bigger and stronger and those not used will become weaker and eventually disappear
Inheritance Any feature of an organism that is improved through use is passed on to its offspring
(Beckett and Gallagher, 2001)
According to Lamarck, evolution occurs due to environmental factors. He believed that organisms change during their lifetime in order to adapt to their environment. When they reproduce those changes are then passed on to their offspring. Lamarck’s theory was disregarded over time because it was based on assumptions. These assumptions included; an organism’s body being adaptable enough to incur changes and these changes being passed on to offspring.
Lamarck’s theory differs to Darwin’s and Wallace’s because they both believed that natural selection would ensure that only species best adapted to their environments will go on to reproduce, resulting in change and improvement amongst the species.
I found that a web based search gave access to lots of information. However I did refer back to a biology book to ensure that the information was accurate as there was a vast amount of information on the topics with varied facts and discussions.
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