BIO SCI 94 Lecture Notes - Lecture 8: Pseudopodia, Nitrogen Cycle, Protist

• School: UC-Irvine
• Department: Biological Sciences
• Course: BIO SCI 94
• Professor: Nancy Burley

Document Summary

Prokaryotes are a paraphyletic group that have high metabolic activity and important roles in the nitrogen cycle. Oldest protist fossil was 2. 1 million years ago. Mitochondria evolved by endosymbiosis; aerobic bacteria and anaerobic protist. Evidence about mitochondria consistent with hypothesis of endosymbiosis: Ribosomes - bacterial ribosomes distinctive from eukaryotic ribosomes. Genome - similar structure like a bacteria circular dna. Hypothesis: alveolate, euglenoids, and stramenopila obtained chloroplasts by secondary endosymbiosis. 1st prediction: 4 membranes; two from cyanobacteria, one from primary endosymbiosis, and one from secondary symbiosis. 2nd prediction: 4 membranes; two inner membranes like cyanobacteria, two outer like eukaryotic. Early protists acquired mitochondria from alpha-proteobacteria and chloroplasts from cyanobacteria. Subsequently, protist lineages are diverse in photosynthetic pigments (plastids) via secondary embiosis and subsequent evolution of plastid dna. Cell to cell adhesion, communication, and specialization. Some offspring can be more resistant to parasites than infected parents. Food scarcity/ high population density linked to switching asexual reproduction to sexual reproduction.