Biology 1

Classification Definitions

Defining Key Words

Heterotrophs - Can't make their own food and have to move around and find things to eat. Eg mammals.

Autotrophs - Make their own food by photosynthesis. Eg plants.

Saprophytes - Feed off dead organisms and decaying material. Eg bacteria. 

Oviparous - Lay eggs. Eg reptiles.

Viviparous - Give birth to live young and are fed milk by the Mother. Eg mammals.

Homeotherms - 'Warm-blooded' as their body temperature is kept constant by homeostasis. Eg mammals.

Poikilotherms - 'Cold-blooded' as their body temperature changes with external temperature. Eg reptiles. 

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Five Kingdoms of all living things:

Plants - Autotrophs

Fungi - Saprophytes

Animals - Heterotrophs

Protoctists - Unicellular

Prokaryotes - Unicellular 

Classifying organisms helps scientists identify the kingdom & to classify the organisms:

Kingdom, Phylum, Class, Order, Family, Genus, Species. (King Phillip Can Order Fancy Gherkins Seperately)

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Classifying Animals

Classifying Animals:

Vertebrates - Have a backbone and internal skeleton

Invertebrates - Have no backbone

How they absorb oxygen - Through lungs (mammals),  gills (fish), or skin (amphibians)

How they reproduce - Internal Fertilisation (mammals), external fertilisation (fish), oviparuous, viviparous.

How they regulate their internal body temperature - Homeotherms (mammals), poikilotherms (reptiles) 

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Organisms are the same species if they can interbreed. Duck species eg mallard & yellow-billed can breed to create a 'hybrid'. 

Ring Species: A group of related populations that live in neighbouring areas. Populations living next to each other can interbreed but poulations further apart cannot. Each colour block represents a different population and the area. 

Pink can only interbreed with purple. Blue can interbreed with purple and teal

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Binomial System

The Binomial System gives every species a 2 part Latin name. First part is the Genus and the second part is the Species. Eg Homo-Sapiens.


  • Helps scientists to communicate and identify species in different languages.
  • Enables scientists to conserve species that are endangered  for two similar looking organisms.
  • Scientists can study species and share information about them by identiying them.
  • Target conservation efforts so we can protect areas that have large variety of different species. Eg Rainforests to prevent a large number of species from being destroyed.

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Organisms of the same species have differences. For example, different hair colours, different heights. Two causes of variation: genes and environment.

Organisms characteristics are determined by the genes inherited for parents so the combining of genes from the Mother and the Father causes genetic variation - no two of the spieces are genetically identical .

Characteristics determined by genes include:

Eye colour, blood group, inherited disorders (Cystic Fibrosis).

Characteristics influenced by environment (Acquired characteristics):

Diet, excercise, temperature, light level, amount of water. 

Characteristics due to both (most things):

Body weight, height, skin colour, condition of teeth, academic/athletic prowess) 

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Continuous or Discontinuous Variation


Vary within a range - there are no distinct categories 

  • Animals - any mass (10st 11)
  • Microorganisms - the width of E. coli bacteria varies.
  • Plants - height of the tree (236cm)


Two or more distinct categories. There are no intermediates.

  • Animals - blood group (A, B, AB or O)
  • Microoganisms - Bacteria are either antibiotic-resistant or not.
  • Plants - Courgette colour (yellow, light green, dark green)

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Extreme Environments

Deep sea:

  • Some fish can emit light from body. The light attracts prey which they then eat. 
  • Fish often have large mouths. Scoop particles of food from the seabed. 
  • Fish often have huge eyes to adapt to the dark and long feelers to locate prey.

Volcanic (hydrothermal) Vents:

  • Chemicals from the vents support bacteria that are able to make their food using chemical energy (Chemosynthesis

Polar Regions: (Polar Bears and Penguins)

  • Thick hair coats thattrap warm layer of air next to the skin and greasy fur sheds water 
  • Big feet spread their weight stopping them from sinking into snow or breaking ice.
  • White fur for camoflauge
  • Compact shade reducin heat loss
  • Thick layer of bubbler for insulation - energy store when food is scarce.
  • Insulating fat and oily feathers 
  • Huddle together to conserve heat
  • Streamlined body to reduce water resistance (swim fast)
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Natural Selection

"Survival of the Fittest". Theory was made by Charles Darwin.

How it works:

  • Most organisms give more birth to more young than can actually survive to adulthood
  • Populations don't increase quickly in size because they have to compete for resources (food)
  • Individuals with characteristics better adapted to environment have better survival chance, more likely to breed successfully.
  • Genes with useful characteristics are passed on the the next generation
  • Some will be less well adapted to environment and will be less likely to survive/reproduce.
  • Over time, there will be a higher proportion with beneficial characteristics
  • Eventually the poorly adapted characteristics may be lost.

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Evolution - the slow and continuous change of organisms from one generation to the next (Natural Selection)

DNA Research Evidence:

  • Evolution suggests all organisms have evolved from common ancestors.
  • Closely related species diverged more recently
  • Evolution is caused by gradual changes in DNA.
  • Organisms that diverged away from each other should have more similar DNA.
  • Eg humans and chimps have similar DNA.

Resistant Organisms Evidence:

  • The poisin warfarin was used to kill rats
  • A certain gene gives rats resistance to warfarin - they are more likely to survive and breed.
  • Now there are rat populations that are resistant to warfarin.

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Scientific Community Validation

Scientists accept the theory of evolution because they've shared evidence to make sure it's valid and reliable.

Three mains ways they do this:

They PUBLISH THEIR WORK in scientific journals. If other scientists can repeat their experiments to get the same results, the scientific community are confident that it's reliable.

Before they can publish their work it has to go through PEER REVIEW. Other scientists read and review their work to check it's valid and that experiments are carried out to their highest standards.

SCIENTIFIC CONFERENCES take place. An easy way for the latest hypotheses and evidence to be shared.

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Speciation = development of a new species.

How it works:

  • GEOGRAPHICAL ISOLATION due to physical barrier eg floods, earthquakes.
  • CONDITIONS on each side may be different. Different characteristics will become more common (Natural Selection)
  • Eventually, they will have changed so much they CAN'T BREED TOGETHER anymore.


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Alleles = Different versions of the same gene.

Different versions of the same gene can give different versions of characteristics eg eye colour.

Since there are two copies of each chromosome, there are two copies of each gene eg you might have two allels the same or two different alleles.



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Genetic Diagrams

Genetic Diagrams = show the possible genes of offspring.

Homozygous = When an organism has two alleles for a particular gene that are the same

Heterozygous = When an organism has two alleles for a particular that are different

Genotype = What alleles you have

Phenotype = The actual characteristic.

  • Letters are used to represent alleles.
  • All cells in an organism have two alleles apart from...
  • Gametes only have one allele.
  • If the alleles are heterozygous, only one can determine what characteristic is present
  • The allele for the characteristic shown is the dominant allele (use a CAPITAL LETTER)
  • The other one is called recessive (use a lower case letter)
  • Both alleles must berecessive for the characteristic of the organism to be recessive (eg cc)
  • Dominant alleles overrule the recessive one if the organism is heterozygous (eg CC or Cc)
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Genetic Diagrams and Disorders

Cystic Fibrosis

  • Genetic disorder caused by the cell membranes.
  • Body produces a lot of thick sticky mucus in the air passages, gut and pancreas.
  • Breathing difficulties, lung infection, malnutrition and fertility problems.
  • Caused by a recessive allele.

Sickle Cell Anaemia

  • Genetic disorder characterised by mis-shaped red blood cells.
  • Red blood cells can get stuck in the capillaries
  • Deprives body cells of oxygen.
  • Tiredness, painful joints and muscles, fever and aneamia.
  • Caused by inheriting two recessive alleles.

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