Feeding Flashcards
Why does life on earth require food?
To maintain normal cellular function and replication and to reproduce.
What is an autotroph and what domains and kingdoms of life are they found in?
Autotrophs are organism that synthesis the food they require for life (but may need to source other nutrients such as Nitrogen from the environment)
They are present in all three domains and the four of the six kingdoms : Bacteria, Archaea, Protists, plantae
NO ANIMALS OR FUNGI
What is an autotroph and what domains and kingdoms of life are they found in?
Heterotrophs are organisms that are unable to make their own food, and so must consume other sources of organic carbon and other nutrients (by consuming other forms of life)
Found in ALL domains and ALL kingdoms of life. And is the EXCLUSIVE mode of feeding for the kingdoms Fungi and Animalia.
Why are autotrophs important and what are the two types?
Autotrophs are the producers of organic energy for all other organisms.
1) Chemoautotrophs - these are bacteria that also synthesis their own organic molecules using the oxidation of inorganic compounds as a source of energy, rather than sunlight
2) Photoautotrophs - these green plants/some bacteria/and algae manufacture all their required organic molecules from simple inorganic molecules using sunlight as the energy source for photosynthesis.
Why are autotrophs important and what are the six types?
Heterotrophs are the primary, secondary, and tertiary consumers.
1) Carnivores - eat animals
2) Insectivores - eat insects
3) Herbivores - eat plants
4) omnivores - eat meat, plants, fungi etc.
5) Scavengers - eat remains of food left by carnivores and herbivores
6) Detritivores - eat soil, leaf litter and other decaying organic matter
What is the functional difference between an autotroph and heterotroph?
Autotrophs are primary producers; heterotrophs are consumers
Why do you think all species of animals and fungi are heterotrophs?
Advantageous state (and thus selection pressure to synthesis own food reduced) but also once the capacity to photosynthesize is lost, it would require a second endosymbiotic event that had a selective advantage
Describe the ancestral heterotrophs?
Earliest life forms were likely single-celled primitive heterotrophs that would have resembled modern day bacteria
They fed by absorbing acid and base molecules in the early organic (c) oceans
This chemical breakdown was a form of fermentation
What is the history of photoautotrophs?
The earliest photoautotrophs were likely photosynthetic bacteria.
These early forms were capable of anoxygenic photosynthesis - a photosynthetic pathway that occurs in the absence of oxygen and does not generate oxygen
Increased levels of oxygen favored oxygenic photosynthesis - photosynthetic pathway that both requires and generates oxygen
Oxygenic photosynthesis evolved about 2.7 billion yrs ago in bacteria that were similar to modern cyanobacteria
Then early eukaryotic cells engulfed photosynthetic bacteria (through endocytosis) resulting in the fist plant cells - endosymbiotic theory
Describe the endosymbiotic theory and what empirical support does it have.
Proposed for the evolution of eukaryotes from prokaryotes over 100 yrs ago but needed electron microscopes to prove
Ancestral prokaryote would have had folds in its membrane and engulfed or absorbed in it, photosynthesis bacteria and aerobic bacteria and these would form and be housed within this ancestral eukaryote
Mitochondria and chloroplast are well known endosymbionts (organelles)
EMPIRICAL SUPPORT:
- Phylogenetically related: Chloroplasts are related to cyanobacteria and mitochondria are related to proteobacteria
- Genome reduced: As organelles, Mitochondria and chloroplast have their own DNA but the genome size is reduced compared to their prokaryote ancestors
- Across species the number of chloroplast can vary
Why have scientists concluded that the earliest lifeform was likely a heterotroph?
To be autotrophic, it would need to have already have evolved a trait that allowed it to synthesize food. It is far more likely that diffusion and osmosis or organic and inorganic substance (from water) was the first mode of obtaining resources
