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8.3Unit 4: Living organisms and classification

Classifying organisms what is a species — Cambridge Checkpoint Biology 0893 Revision Notes & Topical Questions

5 min read 8 parts Lesson 3 of 5 1 quiz

📚 Cambridge Checkpoint Biology 0893 Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Lesson summary

8.3 Classifying organisms what is a species — CHECKPOINT BIOLOGY 0893 notes: Define a species, explain why hybrids such as mules are not a new species, and describe how organisms are classified and named.A species is a group of organisms that are similar and can interbreed to pro…

  • Classification
  • Binomial system
  • A species is a group of organisms that are similar and can interbreed to produce fertile offspring
  • Fertile offspring can themselves reproduce, and infertile (sterile) offspring cannot
  • Members of a species share many characteristics but still show variation
  • Variation between species is large, for example a cat compared with a dog

Section 1 of 8Species

1
A species is a group of organisms that are similar and can interbreed to produce fertile offspring.
2
Fertile offspring can themselves reproduce, and infertile (sterile) offspring cannot.
3
Members of a species share many characteristics but still show variation.
4
Variation between species is large, for example a cat compared with a dog.
5
Variation within a species is smaller, for example different breeds of dog are all one species.

Section 2 of 8Hybrids

Hybrids
A hybrid is the offspring of two different species.
  • A horse and a donkey produce a mule.
  • A lion and a tiger produce a liger.
Hybrids are usually infertile, which shows the parents are different species.
A mule is not a new species.

Section 3 of 8The reproduction test

1
Check whether the two organisms can breed together.
2
Check whether the offspring are fertile.
3
If they breed to give fertile offspring, they are one species.
4
If not, they are different species.

Section 4 of 8Classification

Classification
Classification
Classification sorting organisms into groups based on shared features.
The groups from largest to smallest are kingdom, phylum, class, order, family, genus and species.
The five kingdoms are animals, plants, fungi, protoctists and prokaryotes (bacteria).
Animals are divided into vertebrates and invertebrates.
  • Vertebrates have a backbone and include fish, amphibians, reptiles, birds and mammals.

Section 5 of 8Naming species

1
The binomial system (Linnaeus) gives each species a two-part Latin name: genus then species.
  • Examples are Homo sapiens and Panthera leo.
2
The genus has a capital letter and the species name is in lower case.
3
The name is written in italics, or underlined by hand.
4
Scientific names avoid confusion caused by different common names in different languages or regions.

Section 6 of 8Identifying species

Identifying species
A dichotomous key uses a series of paired questions to identify an organism.
Keys are based on variation in the features of different species.

Section 7 of 8Key terms

TermMeaning
SpeciesA group of organisms that can interbreed to produce fertile offspring.
HybridThe offspring of two different species.
ClassificationSorting organisms into groups based on shared features.
Binomial systemA two-part Latin naming system of genus and species.
VariationDifferences between organisms.
FertileAble to produce offspring.

Section 8 of 8Exam technique

1
Saying a species is animals that look the same — a species can interbreed to produce fertile offspring.
2
Saying the mule is a new species — it is an infertile hybrid of two species.
3
Saying dog breeds are different species — all breeds are one species and can produce fertile puppies.
4
Writing the scientific name as "homo Sapiens" — the genus has a capital letter and the species is in lower case.
5
Forgetting that offspring must be fertile — infertile hybrids do not make the parents one species.

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