PNB 2250 - Exam 1 Questions with Correct Answers Fully Solved Latest 2025
How are plant cells held together? - Answers Plasmodesma
Plasmodesma - Answers Flow of nutrients between cells
How are animal cells held together? - Answers Tight junctions
Tight junctions - Answers Unique connections for animal cells
2 absolute requirements of animals: - Answers 1. Control Systems
2. Distribution Systems
True/False: gene number is proportional to physical structure or complexity - Answers FALSE - it is NOT
proportional
Which fossils do we find the most of? - Answers Newer, marine animals
Extant ancestor of animals - Answers Chaonoflagellates
Examples of convergent evolution - Answers - Flight in insects, bats, birds
- Opposable thumbs in opossums
- Echolocation in whales, bats, shrews
Why is immortality impossible? - Answers The universe does not have an infinite amount of energy
George Wald - Answers Discovered the prevalence of CHONPS - 96% of body mass
4 characteristics of CHONPS - Answers - 2 or fewer electron shells
- strong intramolecular bonds
- double and triple bonds
- maintenance of structure
Animals strive to maintain their internal environment suitable for life, or _____ - Answers Homeostasis
Claude Bernard - Answers discovered homeostasis
Homeostasis - Answers A constant internal environment in the face of a changing external environment
3 examples of components of homeostasis - Answers Body temp.
Blood pH
Blood glucose
, Components of a feedback loop - Answers - Sensor
- Variable
- Output
Feedback Loop: sensor - Answers A protein based biochemical amplifier
Feedback Loop: Output - Answers Change in physiological variable
Most common type of feedback - Answers Negative
Negative feedback - Answers Reducing the change in physiological variables
In the geological past, there were toxic concentrations of: - Answers NH4, CH4, and CO2
Basis of the food chain for all marine life - Answers Phytoplankton
How did phytoplankton create Earth's capability for animal life? - Answers Converted Earth from a
chemical reducing state to an oxidizing state
When did photosynthesis begin? - Answers 2.5 BYA
When did animals appear on Earth? - Answers 1.2 BYA
Cambrian Explosion - Answers Once the Earth became more favorable for animal life, there was a rapid
explosion in animal number and diversity
Possible causes of the Cambrian Explosion - Answers - Hyperoxia
- Prior massive glaciation
- Volcanism
Approximately when was the appearance of all animal phyla? - Answers 540 MYA
Sturtian snowball earth - Answers 717-659 MYA
Ocean surfaces frozen for millions of years
Key events of the Post-Sturtian World - Answers - Rise of algae
- Reduction in cyanobacteria
- Increased ocean nutrients (phosphate)
- Increased atmospheric O2
What began the movement of mantle elements into the biosphere? - Answers Volcanism
How are plant cells held together? - Answers Plasmodesma
Plasmodesma - Answers Flow of nutrients between cells
How are animal cells held together? - Answers Tight junctions
Tight junctions - Answers Unique connections for animal cells
2 absolute requirements of animals: - Answers 1. Control Systems
2. Distribution Systems
True/False: gene number is proportional to physical structure or complexity - Answers FALSE - it is NOT
proportional
Which fossils do we find the most of? - Answers Newer, marine animals
Extant ancestor of animals - Answers Chaonoflagellates
Examples of convergent evolution - Answers - Flight in insects, bats, birds
- Opposable thumbs in opossums
- Echolocation in whales, bats, shrews
Why is immortality impossible? - Answers The universe does not have an infinite amount of energy
George Wald - Answers Discovered the prevalence of CHONPS - 96% of body mass
4 characteristics of CHONPS - Answers - 2 or fewer electron shells
- strong intramolecular bonds
- double and triple bonds
- maintenance of structure
Animals strive to maintain their internal environment suitable for life, or _____ - Answers Homeostasis
Claude Bernard - Answers discovered homeostasis
Homeostasis - Answers A constant internal environment in the face of a changing external environment
3 examples of components of homeostasis - Answers Body temp.
Blood pH
Blood glucose
, Components of a feedback loop - Answers - Sensor
- Variable
- Output
Feedback Loop: sensor - Answers A protein based biochemical amplifier
Feedback Loop: Output - Answers Change in physiological variable
Most common type of feedback - Answers Negative
Negative feedback - Answers Reducing the change in physiological variables
In the geological past, there were toxic concentrations of: - Answers NH4, CH4, and CO2
Basis of the food chain for all marine life - Answers Phytoplankton
How did phytoplankton create Earth's capability for animal life? - Answers Converted Earth from a
chemical reducing state to an oxidizing state
When did photosynthesis begin? - Answers 2.5 BYA
When did animals appear on Earth? - Answers 1.2 BYA
Cambrian Explosion - Answers Once the Earth became more favorable for animal life, there was a rapid
explosion in animal number and diversity
Possible causes of the Cambrian Explosion - Answers - Hyperoxia
- Prior massive glaciation
- Volcanism
Approximately when was the appearance of all animal phyla? - Answers 540 MYA
Sturtian snowball earth - Answers 717-659 MYA
Ocean surfaces frozen for millions of years
Key events of the Post-Sturtian World - Answers - Rise of algae
- Reduction in cyanobacteria
- Increased ocean nutrients (phosphate)
- Increased atmospheric O2
What began the movement of mantle elements into the biosphere? - Answers Volcanism
