Diversity of Life Flashcards
What are unicellular organisms, and why are they important?
Unicellular organisms are single-celled life forms essential to life and evolution. They exhibit tremendous biochemical diversity and play vital ecological and physiological roles.
What are the three major groups of unicellular organisms?
- Bacteria – Prokaryotes with diverse metabolisms.
- Archaea – Prokaryotes distinct from bacteria, often extremophiles.
- Protists – A diverse, polyphyletic group of unicellular eukaryotes.
How are prokaryotes (Bacteria and Archaea) different from protists?
Prokaryotes lack a nucleus and organelles, while protists are eukaryotic, meaning they have a nucleus and organelles.
Why is the term “microbe” not an accurate classification?
Because it groups together very different organisms that are evolutionarily distant despite being small and single-celled.
How are Archaea more closely related to eukaryotes than bacteria?
Eukaryotic nuclear genes originated from Archaea, making them closer relatives than bacteria in terms of genetics.
What is a key difference between bacterial and archaeal cell walls?
Bacterial cell walls contain peptidoglycan, while archaeal cell walls have different biochemical structures.
How do unicellular organisms deal with harsh environments?
Through biochemical adaptations, such as extremophile proteins that resist denaturation, or entering a dormant state to survive unfavorable conditions.
What are extremophiles?
Archaea that thrive in extreme environments like high temperatures, high salinity, or extreme pH.
How do bacteria exchange genetic material?
- Transformation – Absorbing free DNA from the environment.
- Transduction – DNA transfer via a virus (bacteriophage).
- Conjugation – Direct DNA transfer through a pilus.
How do bacteria develop antibiotic resistance?
By acquiring genes through transformation, transduction, or conjugation that encode enzymes to break down antibiotics.
What is endosymbiosis?
A process where a unicellular organism engulfs another and forms a symbiotic relationship, leading to organelles like mitochondria and chloroplasts.
What is primary endosymbiosis?
When a eukaryotic ancestor engulfed a proteobacterium, leading to mitochondria, and later a cyanobacterium, leading to chloroplasts.
What is secondary endosymbiosis?
When a eukaryotic cell engulfs another eukaryote that already contains an endosymbiont, leading to complex plastid structures in certain protists.
Why are prokaryotes essential to ecosystems?
They serve as primary producers (autotrophs), decomposers, and symbiotic partners in nutrient cycling.
How do microbes contribute to human health?
The gut microbiome aids digestion and interacts with the immune system to maintain health.
How have bacteria influenced human history?
Through diseases like tuberculosis and plague, as well as biotechnology innovations like antibiotic production.
How do protists challenge traditional classification?
They are polyphyletic, meaning they do not share a single common ancestor, making them difficult to categorize.
What unicellular organism is considered the closest relative to animals?
Choanoflagellates, which resemble sponge choanocytes and may have given rise to multicellular animals.
What makes multicellular organisms distinct from unicellular ones?
Multicellular organisms consist of specialized cells arranged into tissues, allowing for greater diversity in structure and function. Unlike unicellular organisms, which must perform all life functions within a single cell, multicellular organisms distribute tasks among different tissues and organs.
What are the main groups of multicellular organisms?
Plants, fungi, and animals.
From which ancestral group did plants evolve?
Plants likely arose from protists related to modern green algae.
How do algae differ from plants?
Algae lack true organs and vascular tissues (xylem and phloem). Some, like kelp, can be large but lack structures such as roots, stems, or leaves.
What are bryophytes, and why are they important?
Bryophytes are non-vascular plants that remain small due to their lack of a transport system for water and nutrients.
What key adaptation allowed vascular plants to grow larger?
The development of a vascular system with xylem (water transport) and phloem (nutrient transport).
