Biology II Unit Review

Origins of Life and Evolution, Bacteria and Archaea, Eukaryotic Origins and Diversity, Multicellularity and Evolution, Fungi

When did life begin on earth?

~3.5 billion years ago

What are stromatolites, and why are they significant?

layered structures formed by microbial communities, they provide evidence of life as early as 3.5 bya

What was the Great Oxygenation?

the rise in atmospheric oxygen ~2.4 bya due to photosynthetic bacteria, leading to mass extinction of anaerobic organisms

When did eukaryotic life evolve?

~1.8 billion years ago

What is the significance of multicellularity?

it evolved ~1.3 billion years ago, allowing for more complex life forms

What are the approximate timings for key evolutionary events?

Earth formed

~4.5 bya

Life began

~3.5 bya

Photosynthesis evolved

~3.5 bya

Eukaryotic life evolved

~1.8 bya

Multicellularity

~1.3 bya

Land plants

~470 mya

Tetrapods

~365 mya

Homo sapiens

~200,000 ya

What are key characteristics of Bacteria and Archaea?

they are microscopic, unicellular, lack a nucleus, reproduce asexually, have circular chromosomes

What are the differences between Bacteria and Archaea?

Archaea have ether-linked membrane lipids, histone proteins, and can survive extreme conditions.

Bacteria have peptidoglycan in their cell walls and are sensitive to antibiotics.

What are the similarities between Bacteria and Archaea?

both lack a nucleus, have circular DNA, reproduce asexually, and perform horizontal gene transfer

How do bacteria reproduce?

by binary fission

What are the three types of horizontal gene transfer?

Conjunction, transformation, transduction

Why is bacterial cell size limited?

due to reliance on diffusion for nutrient uptake

What are the sources of carbon for photoautotrophs and photoheterotrophs?

Photoautotrophs: Use CO2 as a carbon source.

Photoheterotrophs: Use organic molecules.

What defines Gram-positive bacteria?

They have thick peptidoglycan walls and produce antibiotics.

What role do bacteria play in human health?

Some are beneficial (gut microbiota), while others cause diseases (e.g., Streptococcus, Staphylococcus).

Why do chloroplasts and mitochondria have small genomes?

Genes were lost or transferred to the nucleus.

How did multiple endosymbiotic events shape photosynthetic eukaryotes?

Different lineages of eukaryotes acquired chloroplasts via primary and secondary endosymbiosis

Why do some eukaryotes lack mitochondria?

They adapted to anaerobic environments and lost their mitochondria

What are the seven major eukaryotic groups?

Opisthokonts, Archaeplastida, Stramenopiles, Alveolates, Rhizarians, Amoebozoans, and Excavates.

What are Archaeplastida?

A group including red algae, green algae, and land plants.

What are Stramenopiles?

A diverse group including brown algae, diatoms, and water molds.

Where have human parasites evolved within eukaryotes?

Groups like Excavates (e.g., Trypanosoma) and Alveolates (e.g., Plasmodium).

Unicellular:

Single-celled organisms.

Simple multicellularity:

Adhesion but little specialization.

Complex multicellularity:

Cell specialization, communication, and tissue differentiation.

What are the six lineages with complex multicellularity?

Animals, plants, fungi (twice), red algae, and brown algae

What is bulk flow?

A mechanism that moves substances over long distances in multicellular organisms.

What are the three requirements for complex multicellularity?

Cell adhesion, communication, and genetic regulation for development.

What structures allow cell communication?

Gap junctions in animals and plasmodesmata in plants.

How do fungi obtain nutrients?

They secrete enzymes and absorb organic molecules (chemoheterotrophs)

What is the structure of fungal hyphae?

Hyphae have chitin cell walls, septa, and form networks called mycelium.

How do fungi impact the global carbon cycle?

They decompose organic material, recycling carbon.

What are mycorrhizae?

Symbiotic relationships between fungi and plant roots.

What are lichens?

Stable associations between fungi and photosynthetic microbes

What are the two types of fungal reproduction?

Asexual (spores, budding) and sexual (plasmogamy, karyogamy, meiosis)

What are the major fungal groups?

Basidiomycetes, Ascomycetes, Zygomycetes, Chytrids, and Glomeromycetes.