4.1

Ecosystems are cyclical
Interdependent
Routinely built up then destroyed
Species
- A group of organisms that can interbreed to produce fertile offspring
- Often members of the same species have similar physical characteristics
  - Ex most dogs have two legs
  - But members of the species do have distinct features
- The gene pools of members of one species would be largely distinct from other species
- A common phylogeny
  - Phylogeny----> Phylogeny is the study of relationships among different groups of organisms and their evolutionary development. Phylogeny attempts to trace the evolutionary history of all life on the planet. It is based on the phylogenetic hypothesis that all living organisms share a common ancestry.
  - Phylogeny--> family tree

Classification of species

By what they eat
Troph- root word
- To eat
Autotrophs
- Provide/ synthesize their own food
- Produce organic molecules from inorganic molecules
- Usually photosynthesis
- Bottom of every food chain
- Exist in really large numbers
- Also called producers
Heterotrophs
- Consume other organisms
- Animals, fungi, some bacteria, some protists
- Consumers
- Obtain organic compounds
  - Proteins, lipids, carbohydrates, vitamins etc.
- Can eat producers or other consumers
Decomposers
- They unlock nutrients stuck in dead organisms
- Food chains are linear, the end needs to return to the ecosystem
- Sustainability is the reason why our ecosystems are able to maintain nutrient cycling methods
- Detritivores
  - Eat non-living organic matter
  - dead leaves, carcasses, feces
  - Eat detritus
  - Ex earthworms, dung beetles
  - Internal digestors
  - Consume what they eat
  - Very different from saprotrophs
- Saprotrophs
  - Eat non living organic matter
  - External digestion
    - Outside their bodies
    - Spray digestive juices unto their food, which breaks it down and they then re absorb the digested materials
  - Ex mushrooms
- Decomposers are very important to ecosystems
- They take the dead things and release the important nutrients for others to use
  - These nutrients can now re-enter the food chain

What is a species?

There are some exceptions to our common definition of species
Ex horse and zebra can interbreed
- Some members of separate species can interbreed
- Horses and zebras are not considered to be the same species because their offspring are not fertile
- To be able to successfully breed, two species need to have the same or similar number of chromosomes, and similar genes so this is very rare
Another exception
- Some members of the same species do not interbreed because they are separated by large distances
  - Ex human begins in Africa and Asia often do not interbreed, but are still human beings, the same species
  - If we put them together they could interbreed
Some species reproduce asexually and therefore do not interbreed
- We cannot put two bacteria together and see if they produce fertile offspring, sexual reproduction is not a part of their life cycles
- Genetics would help determine if they are of the same species
Some members of species are infertile
- This interbreeding definition does not work, but they are still members of the species
Hybrids
- Offspring of two similar but separate species
- Most of their offspring are infertile, but there are exceptions
- Ex horse+ donkey is a mule
- They generally do not occur in nature
- These animals generally do not find the other species attractive
Formation of new species
- Groups of species that have been separated for long periods of time often evolve to better suit their new environment
- Over time, they lose their ability to reproduce with each other ---> new species
- Happens over million of years
- Separation by a canyon, or sea, flooding, volcanic eruption etc.