Although individuals within a species are very similar, they are not identical. A species is a group of organisms that can interbreed with each other to produce offspring. For example, different breeds of dogs can interbreed successfully. Even though they seem different in appearance, they are from the same species.

  • species - a group of organisms that can interbreed with each other and produce offspring.
  • interbreed: to mate, or use sexual reproduction
  • offspring - the next generation, the 'babies' produced from two parents
  • inherit - to get from your parents

In the dog species there are many different breeds.

Variation and Survival
Variation occurs within all species. Much of this variation comes from the differeneces in the genetic material (chromosomes) that each individual inherits from their parents. Other variations come from environmental factors such as sun exposure and differences in diet.
The organisms best suited to their environment are most likely to produce offspring. These organisms have favourable characteristics that make it easier for them to survive and reproduce. Their offspring will inherit these favourable characteristics. Over several generations, individuals with favourable characteristics will become the most common. The favourable characteristics have been 'naturally selected'.
Variation in a species in particularly important if the environment changes. Some individuals will have characterisitics that are favourable, allowing the species to survive the environmental change.
Variation in a ladybug species. Which one do you think would suit the environment the best and camouflage into the background?

1. Write the definitions for species, interbreed, offspring and inherit in your wordlist.
2. Copy the information from "Variation and Survival" into your notes in your book or OneNote.
3. Answer the following questions in your book or OneNote.
Questions: 1. Choose three different breeds of dog and describe how they vary (are different) from one another.
2. Describe two different factors (things) that can cause variation in a species.
3. Use the example of the peppered moth (from page 4) to explain how variety in a population can change as a result of an environmental change.