PYTR Class

Learning Objectives

1. Summarise the information about the term biosphere and biomes
2. Describe the concept of species using a case study of the arctic seagulls
3. Outline the limitations of the concept species
4. [Skill]: Apply dichotomous key

---

The Biosphere

• Biome is a large area characterised by:
  1. vegetation
  2. soil
  3. climate
  4. wildlife. 

• Five major types of biomes are:
  1. aquatic
  2. grassland
  3. forest
  4. desert
  5. tundra

• Some biomes can be further divided into the following categories:
  1. freshwater
  2. marine
  3. savanna
  4. tropical rainforest
  5. temperate rainforest
  6. taiga

---

Concept of Species

Definition:

“a species is a group of organisms that can interbreed and produce fertile offspring”

• Individual organism is a member of a species
• Sometimes, two species breed together to produce hybrid offspring. A hybrid may survive to adulthood but cannot produce viable gametes and so is sterile. Examples include:
  • Horse (Equus caballus) + donkey (Equus asinus) à Mule
  • Male tiger (Panthera tigris) + lioness (Panthera leo) à Tigon
  • Female tiger + male lion à Liger

Limitation to the species concept:

• Cannot clarify whether geographically isolated populations belong to the same species
• Cannot classify species in extinct populations
• Cannot account for asexually reproducing organisms
• Cannot clearly define species when barriers to reproduction are incomplete

---

DNA profiling in dichotomous keys

• Organisms can also be classified based on their specimens in a herbarium 
• Museums often use DNA profiling techniques to identify differences between specimens.
  • More accurate way of determining the identity of an organism than using only its physical appearance.