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2.3Unit 4: Living organisms and classification

What is a species

5 min read 6 parts Lesson 3 of 5 1 quiz

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2.3 What is a species — CHECKPOINT BIOLOGY 0893 notes: Define a species, explain how variation makes appearance unreliable, and describe how scientists decide whether organisms belong to the same species.Scientists group living organisms into different kinds, and each kind is cal…

  • Binomial name
  • Scientists group living organisms into different kinds, and each kind is called a species
  • Species = a group of organisms that can reproduce together to produce fertile offspring
  • Offspring = the young produced by reproduction, which belong to the same species as their parents
  • Fertile = able to reproduce and produce offspring
  • Infertile = not able to reproduce, although the animal is healthy and alive

Section 1 of 6Species

  • Scientists group living organisms into different kinds, and each kind is called a species.
  • Species a group of organisms that can reproduce together to produce fertile offspring.
  • Offspring the young produced by reproduction, which belong to the same species as their parents.
  • Fertile able to reproduce and produce offspring.
  • Infertile not able to reproduce, although the animal is healthy and alive.

Section 2 of 6Variation within a species

  • Members of a species share the same characteristics but are not identical.
  • Variation = the differences between individuals of the same species.
    • Some Indian elephants have straighter tusks than others.
    • Their pink skin markings are in different places.
  • Organisms of the same species usually look similar to one another and different from other species.
  • Because of variation, appearance alone can make it hard to decide whether two organisms are the same species.

Section 3 of 6The reproduction test

  1. Ask whether the two organisms can reproduce with one another.
  2. If they can, check whether the offspring are fertile.
  3. If they reproduce and have fertile offspring, they are the same species.
  4. If they cannot reproduce, or the offspring are infertile, they are different species.
  • Each species reproduces only with members of its own species.
    • Indian elephants reproduce only with other Indian elephants, not with African elephants.
  • Organisms from different species cannot usually reproduce with one another.

Section 4 of 6Offspring of different species

  • Very rarely, organisms of different species reproduce together, for example in a zoo when no member of their own species is available.
  • A male lion and a female tiger can produce a liger.
    • Ligers are healthy animals.
    • Ligers cannot reproduce, so they are infertile.
  • Lions and tigers are different species because their offspring are infertile.
  • A hybrid is the offspring of two different species, for example a mule from a horse and a donkey, and hybrids are usually infertile.

Section 5 of 6Comparing two species

  • A specimen is a sample of an organism that is examined.
  • Compare two species by listing similarities first and then differences.
    • Indian and African elephants both have a trunk, tusks, four thick legs, grey skin and a tail.
    • African elephants are larger with much larger ears, and the back of an Indian elephant curves upwards.
  • Safety
    • wash hands carefully after handling live organisms.

Section 6 of 6Naming species

  • Every species has a two-part scientific name (the binomial system): the genus first and then the species.
    • Examples are Panthera leo and Homo sapiens.
  • The genus begins with a capital letter and the species name has small letters.
  • The name is written in italics, or underlined when written by hand.
  • One system avoids confusion between the different local names in different languages.
  • A breed, such as a Labrador dog, is a type within one species and not a separate species.

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