Chapter 22
In a phylogenetic tree, what does a branch point (node) represent?
The most recent common ancestor
The three types of symbiosis are...
mutualism, commensalism, and parasitism
What process allows Eukaryotic cells to engulf food particles into vesicles?
phagocytosis
In which of the following groups did multicellularity evolve independently? Animals only, Plants and Fungi, Algae only, or All of the above
All of the above
Which fungal structure provides the large surface area needed for nutrient absorption?
Hyphae
Which type of group contains a common ancestor and all of its descendants?
monophyletic
What group of prokaryotes includes species that thrive in very salty environments?
Halophiles
What is hypothesized to be the sister group to Eukarya?
Archaea
What three processes are required for complex multicellularity?
Cell Adhesion, Communication, Genetic Programming
All fungi have sexual reproduction.
False
What does a paraphyletic group include and provide an example.
Common ancestor and some of its descendants; protists, dinosaurs, etc
A researcher adds purified DNA containing an antibiotic resistance gene to a culture of non-resistant bacteria. After incubation, some bacteria survive on antibiotic plates. Which process most likely explains how these cells acquired the resistance gene?
Transformation — uptake of naked DNA
Morphological and molecular evidence point to __________ as the sister group to animals.
Choanoflagellates
During early embryonic development in animals, rapid mitotic divisions (cleavage) occur without significant growth, producing a hollow sphere of cells. This stage precedes gastrulation, when germ layers begin to form. What enables this process in animals?
Animal cells do not have cell walls, so they can move
A soil ecologist observes that fungi in a forest floor spread extensively through the soil, increasing contact with organic matter and plant roots. This network of filaments enables efficient nutrient absorption and forms mutualistic associations such as mycorrhizae. What is this interconnected structure called?
Mycelium — the collective network of hyphae that maximizes surface area for absorption and ecological interactions.
The molecular clock hypothesis is powerful in estimating divergence times. Why is it particularly useful when fossil evidence is scarce, and what is its key underlying assumption?
Molecular mutations accumulate at relatively constant rates
Assumes mutation rates can be used as “clocks” for divergence time estimates.
A medical team isolates a bacterial strain from a patient infection. The cells appear pink after a Gram stain. The strain is more resistant to penicillin than other bacteria they are studying. What reasoning would best explains both the staining result and the increased antibiotic resistance?
Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane containing lipopolysaccharides, which blocks many antibiotics and causes them to stain pink.
Scientists sequenced the DNA of an organelle and found it to be circular, with genes most closely related to those of α-proteobacteria. The organelle is also surrounded by a double membrane and contains its own ribosomes. Based on these data, which organelle is this? How did it form?
Mitochondrion — supported by genomic, structural, and biochemical evidence of its proteobacterial ancestry. Endosymbiosis
In plants, cytoplasmic connections allow direct exchange of signaling molecules across rigid cell walls. In animals, specialized protein channels connect adjacent cells for rapid communication. Which structures perform these roles in plants and animals, respectively?
Plasmodesmata in plants; gap junctions in animals
During fungal sexual reproduction, two haploid cells first fuse their cytoplasm but keep their nuclei separate, resulting in a prolonged dikaryotic (n+n) stage. Only later do the nuclei merge to form a diploid zygote nucleus. Which terms describe these two sequential fusion events?
plasmogamy; karyogamy
The principle of maximum parsimony assumes evolutionary events are minimized. How might this principle conflict with cases of convergent evolution?
Parsimony can be misleading when convergent evolution produces similar traits independently (e.g., wings in birds vs. bats).
A wetland restoration project is struggling because plants show severe nitrogen deficiency despite adequate sunlight and water. Soil analysis reveals very low populations of symbiotic bacteria such as Rhizobium. The restoration team considers adding industrial fertilizer. Which biological process is missing in this ecosystem and which organisms normally carry it out?
The missing process is nitrogen fixation, the conversion of N₂ gas into ammonia (NH₃) and it is carried out by bacteria and archaea.
Comparative genomics reveals that chloroplast DNA in Archaeplastids is similar to a photosynthetic bacterial genome. Additionally, chloroplasts are surrounded by two membranes. Which prokaryote was engulfed during this primary endosymbiotic event? How does the number of membranes provide evidence for the nature of this event?
The symbiont was a cyanobacterium.
Two membranes indicate direct engulfment of the prokaryote: one from the cyanobacterium and one from the host phagosom
Fossil evidence shows that large, multicellular eukaryotes appear in the record roughly 600 MYA. Molecular and physiological studies reveal that complex multicellularity requires high-energy metabolism to support bulk flow, specialized tissues, and signaling networks. Which atmospheric change enabled the evolution of complex multicellularity?
A rise in atmospheric oxygen levels
Place the following fungal innovations in the correct evolutionary order: 1. Septa 2. Hyphae 3. Fruiting Bodies 4. Chitin in cell walls
4, 2, 1, 3