Biology Exam Notes

Living Things: organisms exist in a variety of shapes and sizes and can be found just about everywhere Each type of organism has special structures that allow it to survive; these are called adaptations  Different adaptations are required for different environments biodiversity refers to all forms of life evidence suggests that the first life forms arose in the seas as simple organisms, similar to bacteria, 4 billion years ago

Living in Water: all living things are composed of one or more cells if the concentration of cell chemicals becomes too high or too low, the organism dies Water is an ideal environment for organisms Water is a stable living place organisms can grow to large sizes without skeletons due to water buoyancy  representatives of all groups of organisms live in water prokaryotes and protists are only found in water oxygen doesn't dissolve well in water

Living on Land: on land light is abundant and not blocked by anything (i.e. water) carbon dioxide is essential for photosynthesis  plants emerged 400 million years ago problems faced: obtaining enough water, preventing water loss maintaining a moist surface, supporting body against pull of gravity,carrying out reproduction, withstanding severe fluctuations of temperature  fungi, plants and vertebrae's are the most successful organisms on land

Making Sense of the Diversity of Life Forms: it is a human characteristic to group things the knowledge that most people have of organisms around them is restricted to those plants and animals that have a direct bearing on their lives there are at least 5 million species on earth of all the species that have lived, 99% are extinct the kind of classifications of organisms used depends on the needs of the organisers of the system any system of classification is only an aid to understanding and communication and will continue to change as new information comes to hand 

The Basics of Biological Classification: the science of naming and classifying living things is called taxonomy Biologists are not only concerned with the similarities and differences between groups but also the relationships between them Taxonomists are concerned with the evolution of species Accurate classification of organisms can also lead to a prediction

The Species: Species means 'kind' in Latin A species is generally defined as a group of similar organisms who can interbreed although the species concept works well with sexually producing animals it presents some problems  in asexual organisms different species are given scientific names every type of organism is given a two word scientific name = BINOMIAL  Latin or Ancient Greek are used when naming organisms as they are 'dead languages' and won't change Better known organisms have more common names A scientific name consists of a genus name and a specific name The scientific name is typed in Italics but underlined when handwritten when referring to a particular group, use the genus name the person who first describes a species has the right to name it

Grouping Species: related species are grouped together into genera, related genera into families, related families into orders, related orders into classes, related classes into phyla and related phyla into kingdoms within each group there may be subdivisions  Members of species who differ are put into varieties  members of a particular species may be geographically isolated and they are called subspecies or races diagnostic features are characteristics which differentiate one group from all others

Features Used in Classification: biologists group species to reflect the relationships between them groups are about evolutionary history studying fossils shows new information the general appearance of organisms gives important clues to the classification Structure can be misleading organisms with a common structure are called homologous structures Organisms that have a similar superficial appearance but show no signs of relatedness are called analogous structures it can be hard to differentiate between the two and other characteristics are usually needed comparisons with fossils provides further evidence  If in the early development two organisms look the same, or show a similar pattern, they are probably related

The Kingdom Debate: not all organisms fit into 'plant or animal' Plants and animals alone are known as the two kingdom system more systems, such as the three, four and five kingdom systems have been introduced The five kingdom system is the one used today The five kingdoms are Monera, Protista, Fungi, Plantae and Animalia  A recent development places organisms into domains based on their genetic make-up The three domains are Archea, Eubacteria and Eukarya.

Identification Keys: Biologists often use keys or diagrams to help them identify different organisms observable features are used to separate organisms into smaller groups until the organism can be identified by its unique features alternatives in keys should be vary comparative (e.g. legs, no legs) keys with only two alternatives at each stage are known as dichotomous keys  

Summaries:

Summaries: biodiversity refers to the organisms that inhabit the earth first living organisms are believed to have evolved from the sea biological classification is the evolutionary system of grouping organisms A species is a natural group of organisms which freely interbreed and produce fertile offspring a key is a tabular or flow diagram system for identifying organisms quickly and easily

Definitions: Radial Symmetry- the arrangement of body parts around a central axis, if halved will make a mirror image bilateral symmetry- a body form where right and left sides will form a mirror image pentameric symmetry- the arrangement of a body around a central axis with five spokes Body cavity- animals with three layers of ebryonic cells may develop a body cavity.  Segmentation- animals with three layers may be segmented.  exoskeleton-  structural support ( skeleton) found on the outside endoskeleton- skeleton found within the animal pentadactyl limb-  limb structure found in four legged animals with five digits

Summary: animals are heterotrophic eukaryotes which typically ingest food Movement typically achieved by special cells most reproduce sexually classification based on of cell layers present

formation of the earth: life is said to have developed on earth 4 billion years ago the universe is approximately 4.6 billion years old heat caused elements to form little or no oxygen was available  for thousands of years rainstorms covered the earth erosion caused crust of minerals to dissolve into water collected in basins ; thus, the oceans were created

the first life forms: it is suggested that methane, carbon dioxide and ammonia from the atmosphere dissolved and landed in the oceans this may be how the first organic life forms were created the first living cells were organised into groups of chemicals which could reproduce they were very simple chemicals bound together by a membrane which separate them from their surroundings these type of cells are prokaryotic  present day prokaryotic cells are things like bacteria the first living life forms came into being through abiogenesis (non living things)  these organisms were heterotrophic (requiring organic compounds of carbon and nitrogen for nourishment)   or chemosynthetic (synthesis of carbohydrate from carbon dioxide and water; limited to certain bacteria and fungi.) chemosynthesis exists in two forms: fermentation (molecules are absorbed then broken down to produce energy) or sulfate reaction (when energy is produced by the removal of oxygen) the evolution of the energetically more efficient process of photosynthesis represented an important breakthrough

Experimental Evidence for the Origins of Life: all known amino acids have been produced in a laboratory when oxygen is introduced, possible element formation is limited this suggests that the first life forms were anaerobic heterotrophs   recent experiments have shown that simple molecules can form more complex molecules when dripped onto hot sand, clay or rock scientists have produced 'droplets' of chemicals which can respond to different environmental situations

Development of the Eukaryotic Organism: one of the molecules that formed early on was chlorophyll  organisms containing this molecule were able to produce their own food this released oxygen into the atmosphere  eventually mutations arose in some of these cells, enabling them to use the oxygen to release the energy from their molecules most scientists accept the idea that photosynthetic and other cells were engulfed (swallowed up) by larger prokaryotes. they were not destroyed, they just remained within the larger cells how the nucleus formed is debatable  one view is that the cell membrane began to fold another is that it was formed by engulfing another prokaryote Archea and Eubacteria arose independently as the earliest life forms  Archea contains prokaryotic life forms that are found in extreme conditions The Eubacteria are a very diverse group mutations in the nucleic acid of the original organisms resulted in new life forms  these new life forms had effects on the environment gradual changes in the organisms over time, originating from the mutations, are termed evolution organisms that have features that enable them to survive have adapted to the environment if they do not posses these adaptations it is likely they will die

Fossil Evidence: the exact origin of life on earth will never be known scientists only estimate when, where and why techniques have developed for discovering the age of rocks and fossils to be preserved an organism must be buried in sand, slit or clay to prevent decay most organisms that die will not become fossils and there are gaps in fossil history the oldest evidence for life on earth is said to be 3.5 billion years old fossil records show a progression from simple organisms, to complex ones animals were the first multicellular organisms to appear, followed by fungi and subsequently, plants members of all groups currently still exist

development of Protista: modern protists developed from Eukaryotic cells they bear little resemblance to their ancestors  millions of years of refinement and adapting to suit environmental conditions three basic types of Protists: - Protozoa, Algae and moulds

Animal Features: animals are multicellular and heterotrophic organisms  more than 1.5 million species of animals have been described 95% don't have a backbone 1 million of the animals discovered are insects 10 thousand new insects are discovered annually  many also become extinct  early fossils indicate that the animals have an ancient origin no evidence of the sequence in which the various groups arose

Trends in Animal Development: the further development of the Eukaryotic organisms took place over the last 2 billion years ago  it is most likely animals developed from amoeboid protozoans  amoeboids have a flex ible cell membrane nutrients taken in must be released the first step in the formation of animals was a mechanism to maintain contact between cells innovation was added to innovation, each allowing exploitation of a different resource

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