Scientists consider __________ to be a fact because the fossil record contains clear evidence that species have changed with time
Scientists consider **evolution** to be a fact because the fossil record contains clear evidence that species have changed with time.
Which of the following is/are required for the metabolism of life on Earth?
Select all that apply, but choose only those that are required for all known forms of life on Earth.
Responses
sunlight
sunlight
extremophiles
extremophiles
an energy source
an energy source
a carbon source
a carbon source
liquid water
liquid water
carbon dioxide
The requirements for the metabolism of **all known life on Earth** are:
– ✅ **an energy source**
– ✅ **a carbon source**
– ✅ **liquid water**
The others (**sunlight, extremophiles, carbon dioxide**) are not universal requirements.
If we discover life elsewhere, in which of the following ways is it most likely to differ from life on Earth?
Responses
It will evolve through a mechanism different from natural selection.
It will evolve through a mechanism different from natural selection.
It will not have metabolism.
It will not have metabolism.
It will use a different genetic code.
It will use a different genetic code.
It will not need a liquid medium (such as liquid water).
It will not need a liquid medium (such as liquid water).
It will not be made from any cell-like units.
The most likely difference is:
**✅ It will use a different genetic code.**
Natural selection, metabolism, a liquid medium, and cell-like structures are expected to be universal features of life, but the specific genetic code (like DNA/RNA bases on Earth) could vary elsewhere.
Consider the table in the video showing metabolic sources for life (which is a shortened version of Table 5.1 in your textbook). When it says that some organisms get carbon or energy from organic compounds, this basically means they get it through __________.
Responses
metabolism of carbon dioxide
metabolism of carbon dioxide
reactions involving chemicals such as iron, sulfur, and ammonia
reactions involving chemicals such as iron, sulfur, and ammonia
converting sunlight to energy through photosynthesis
converting sunlight to energy through photosynthesis
eating other organisms
That basically means they get it through **✅ eating other organisms**.
The large molecular components of cells fall into four main classes: carbohydrates, lipids, proteins, and nucleic acids. Match each of these with one of the roles it plays in cells.
Put responses in the correct response input area to answer the question. Select a response, navigate to the desired input area and insert the response. Responses can be selected and inserted using the space bar, enter key, left mouse button or touchpad. Responses can also be moved by dragging with a mouse.
carbohydrates
Currently contains form structure and catalyze reactions.
lipids
Currently contains form membranes.
proteins
Currently contains supply energy.
nucleic acids
Currently contains encode heredity.
Here’s the correct matching:
– **carbohydrates** → supply energy
– **lipids** → form membranes
– **proteins** → form structure and catalyze reactions
– **nucleic acids** → encode heredity
Another piece of evidence for the common ancestry of all life on Earth is the fact that ________.
Responses
all life ultimately depends on sunlight for energy
all life ultimately depends on sunlight for energy
all life on Earth requires oxygen to survive
all life on Earth requires oxygen to survive
all living cells use ATP to store and release energy
all living cells use ATP to store and release energy
all living cells require a source of carbon and a source of energy
The correct answer is:
**✅ all living cells use ATP to store and release energy**
What do we mean when we say that living organisms display order?
Responses
Individuals within a species always have a particular birth order, with some born before others
Individuals within a species always have a particular birth order, with some born before others
Different species arose one after another in time.
Different species arose one after another in time.
Cellular structures can be arranged in order of size
Cellular structures can be arranged in order of size
The structures of living organisms display patterns rather than being arranged randomly.
The correct answer is:
**✅ The structures of living organisms display patterns rather than being arranged randomly.**
Charles Darwin is famous for having ________.
Responses
discovered the role of DNA in heredity
discovered the role of DNA in heredity
been the first to propose a hypothesis designed to explain how evolution occurs
been the first to propose a hypothesis designed to explain how evolution occurs
proposed that species evolve through time
proposed that species evolve through time
proposed a model of how evolution occurs that has withstood careful scientific testing and examination
The correct answer is:
**✅ proposed a model of how evolution occurs that has withstood careful scientific testing and examination**
Biologists create the tree of life – a map of relationships between species – by comparing their DNA or the precise structures of molecules coded for by DNA. A simplified version is shown below. Label the three locations on the tree from 1-3 based on how closely related they are to animals with 1 being most closely related and 3 being least.
Without the figure in front of us, I’ll rely on the standard **tree of life** structure:
– **1 (most closely related to animals):** **Fungi**
– **2 (middle distance):** **Plants**
– **3 (least related):** **Bacteria/Archaea**
👉 Animals and fungi share a more recent common ancestor than either does with plants, and all three are much more closely related to each other than to bacteria.
Do you want me to sketch a simple tree diagram so it’s clearer?
The treees are arrchae, bacterian and eukarya
Got it — if the tree is showing the **three domains of life** (Archaea, Bacteria, Eukarya), then in terms of how closely related they are to **animals** (which are eukaryotes):
– **1 (most closely related): Eukarya**
– **2 (middle): Archaea**
– **3 (least): Bacteria**
✅ Animals belong to **Eukarya**, and molecular evidence shows **Archaea are more closely related to Eukarya than Bacteria are**.
A strand of DNA has the following sequence of bases: ATG TAC TGA
What is the sequence of messenger RNA bases that the above sequence would pair with?
DNA: **ATG TAC TGA**
mRNA pairs with complementary bases:
– DNA **A** → RNA **U**
– DNA **T** → RNA **A**
– DNA **G** → RNA **C**
– DNA **C** → RNA **G**
So:
**ATG TAC TGA**
→ **UAC AUG ACU**
✅ The messenger RNA sequence is **UAC AUG ACU**.
Does the theory of evolution satisfy the three hallmarks of science described in your textbook?
Responses
No, because we cannot go back in time to observe evolution happening.
No, because we cannot go back in time to observe evolution happening.
No, because evolution does not make testable predictions.
No, because evolution does not make testable predictions.
No, because it has not been verified in enough different ways.
No, because it has not been verified in enough different ways.
Yes
The correct answer is:
**✅ Yes**
Evolution satisfies all three hallmarks of science: it seeks explanations for observed phenomena, makes testable predictions, and has stood up to repeated testing and verification.
What testable predictions?
Good question. Here are some **testable predictions of evolution** that scientists have confirmed:
1. **Fossil sequences** → Transitional forms should appear in the rock record in the correct chronological order (e.g., discovery of *Tiktaalik* between fish and amphibians).
2. **Genetics** → Organisms that share a more recent common ancestor should have more DNA in common (e.g., humans and chimps share ~98–99%).
3. **Vestigial structures** → Evolution predicts leftover traits from ancestors (e.g., whales have tiny pelvic bones despite no hind limbs).
4. **Observable evolution** → Species should change over time in measurable ways (e.g., bacterial resistance to antibiotics, Darwin’s finches evolving beak sizes).
5. **Biogeography** → Species on islands should resemble nearby mainland relatives, not distant ones (e.g., marsupials in Australia).
👉 These predictions could have been falsified if the evidence went the other way — but instead, the data keeps confirming evolution.
Want me to boil these down into the **exact 3–5 predictions** your textbook likely emphasizes?
Barely scraping by that definition I think., Perhaps on bacteria or some other very fast replicating organism. As evolutions take thousands of years for ,most animals.
Exactly — you’ve nailed the tension.
For **long-lived animals**, we can’t just sit around for thousands of years waiting for the data. But evolution is still **testable** because:
– **Short-term, rapid examples exist**: bacteria, viruses, fruit flies, and even finches show measurable changes within years or decades.
– **Long-term predictions rely on records**: fossils, DNA, and geology act as “snapshots in time.” If, say, rabbits had turned up in Cambrian rocks, that would have flat-out falsified evolutionary theory.
– **Ongoing patterns**: resistance in microbes, pesticide resistance in insects, and artificial selection in crops/animals demonstrate the same mechanisms that drive long-term evolution.
So yeah — it’s not like watching a mountain erode in real time. We catch the quick stuff directly, and the slow stuff is reconstructed with hard evidence that either confirms or falsifies the predictions.
Would you like me to contrast **microevolution (observable now)** vs. **macroevolution (inferred from records)** in one tight table?
But these predictions are really measuring natural selection – a key tenet – but is that really how evolution works?
You’ve put your finger right on the philosophical sore spot.
– **Natural selection** is the *mechanism* Darwin described — heritable variation + differential survival = gradual change.
– **Evolution** is the broader *pattern of change in populations over time*.
Selection explains a lot, but not everything. Other mechanisms matter too:
– **Genetic drift** → random changes in small populations.
– **Gene flow** → migration and mixing between populations.
– **Mutations** → the ultimate source of new variation.
– **Sexual selection** → traits favored for mating success, even if maladaptive otherwise.
– **Symbiosis & horizontal gene transfer** → especially in microbes, entire genes jump between species.
So, when we test “evolution,” we’re not just testing natural selection. We’re testing whether **populations change through any of these mechanisms**. Natural selection just happens to be the easiest to observe and the most powerful driver in many cases.
If you want, I can lay out a **flow hierarchy**: “Evolution (pattern)” → “Mechanisms (selection, drift, mutation, etc.)” → “Testable predictions at each level.” Would that help tighten the picture?
During the mid twentieth century, three competing models were advanced to explain the Moon’s existence. What were the main arguments against each one? Labels can be sorted into more than one category.
Joint Formation Capture Splitting ; Responses: Gravity interact would disrupt, density difference betw e and m, improbable. more that one response is expected
Here’s how the arguments against each model line up:
**Joint Formation (Earth & Moon formed together)**
– ❌ Density difference between Earth and Moon (Moon has much smaller iron core, doesn’t fit if both condensed from same material).
**Capture (Moon formed elsewhere, then was captured by Earth’s gravity)**
– ❌ Gravity interaction would disrupt (an object that large passing by would either escape or crash, not settle neatly into orbit).
– ❌ Improbable (the odds of a stable capture are extremely low).
**Splitting (Moon split off from a rapidly spinning Earth — the “fission” hypothesis)**
– ❌ Improbable (physics shows Earth couldn’t have spun fast enough without flying apart).
👉 That’s why the **giant impact hypothesis** became the accepted explanation later: it avoids those contradictions.
It is 2082, and we discover biosignature evidence for a lifeform on exoplanet TRAPPIST-1e that uses the infrared light of the star and CO2 gas from the planet’s dense atmosphere to drive its biochemistry. What metabolic classification would this organism be?
Responses
photoheterotroph
photoheterotroph
chemoheterotroph
chemoheterotroph
photoautotroph
photoautotroph
chemoautotroph
The organism you described on **TRAPPIST-1e** would be classified as a:
**✅ Photoautotroph**
**Reasoning:**
– **“Photo–”** → It uses **infrared light from the star** as its energy source. That’s photosynthesis (just with IR instead of visible light).
– **“–autotroph”** → It uses **CO₂ from the atmosphere** as its carbon source, not organic molecules.
The other options don’t fit:
– **Photoheterotroph** → would require organic carbon.
– **Chemoheterotroph** → uses chemicals for energy and organic carbon.
– **Chemoautotroph** → uses inorganic chemicals for energy, not light.
So the correct classification is **photoautotroph**.
Let’s discuss this table and how to use it
Perfect — this is the **genetic code table** (codon table). Let’s walk through how to use it step by step:
—
### 1. What it shows
– Each **codon** is a sequence of **3 bases (nucleotides)** in RNA (A, U, G, C).
– Each codon corresponds to a **specific amino acid** — the building blocks of proteins.
– Some codons are **start** (initiate protein synthesis) or **stop** (end protein synthesis).
⚠️ Note: The table you posted uses **DNA bases (A, T, C, G)**, but in mRNA the **T’s become U’s**.
—
### 2. How to read it
– **First base** (left side of the table).
– **Second base** (top row).
– **Third base** (right side).
For example:
– Codon **ATG** → first base **A**, second **T**, third **G** → that gives **Met (Methionine)**, the **start codon**.
– Codon **TAA** → first **T**, second **A**, third **A** → that gives a **stop codon**.
—
### 3. Why it matters
– The codon table is **universal** (with very few exceptions): bacteria, plants, humans — all use the same code.
– It’s what lets DNA → mRNA → protein happen consistently across all life.
—
### 4. Practice example
If your DNA sequence is: **ATG TAC TGA**
– mRNA would be: **UAC AUG ACU**
– Using the codon table:
– **AUG** = Start codon / Methionine
– **ACU** = Threonine
– **UAC** (would normally be Tyrosine, but here it’s before the start codon so it’s not translated)
So the protein made would be **Methionine–Threonine** (then stop).
—
Do you want me to make you a **step-by-step codon decoder cheat sheet** (DNA → mRNA → codon → amino acid), so you can apply it to any sequence instantly?
A mutation occurs to a single base in the amino acid Threonine – ACC. Sort the two possible mutations below as more or less damaging. For reference, the chart below shows the coding for different amino acids.
Let’s analyze your example: the codon **ACC** codes for **Threonine**.
Now, a **point mutation** can change one base. Let’s look at two possible cases:
—
### 1. Mutation that changes ACC → ACA (or ACG or ACU in RNA)
– All of these still code for **Threonine** (check the table).
– This is called a **silent mutation** (no amino acid change).
– **Effect:** **Less damaging** — protein function likely unchanged.
—
### 2. Mutation that changes ACC → something else, e.g. **AAC**
– AAC codes for **Asparagine** (a completely different amino acid).
– This is a **missense mutation**.
– **Effect:** **More damaging** — the protein now has a different building block, which may disrupt its structure or function.
—
✅ **Sorting:**
– **Less damaging:** Base substitutions that keep the codon as Threonine (silent mutation).
– **More damaging:** Base substitutions that change the codon to another amino acid (missense mutation), or worse, into a stop codon (nonsense mutation).
Would you like me to build you a **small mutation impact chart** (ACC → each of the 9 possible single-base mutations, with their amino acid outcome and damage severity)?
ACC- CCC
Good — let’s check this specific mutation:
– **Original codon:** **ACC** → Threonine
– **Mutated codon:** **CCC** → Proline
—
### Impact
– This is a **missense mutation**: the amino acid changes from threonine (polar, somewhat flexible in proteins) to proline (rigid, often introduces kinks in protein chains).
– Proline’s unusual structure can **disrupt protein folding** more severely than many substitutions.
👉 Therefore: **This is more damaging** compared to a silent mutation like ACC → ACA.
Do you want me to map **all nine single-base changes of ACC** (each possible mutation at each position) so you see which ones are silent vs. damaging vs. stop?
Is it that mutations that are horizontal are less damaging that switching rows?
You’ve spotted the *pattern* in the codon table. Let’s unpack it:
– In the **codon chart**, codons in the **same “box” or row cluster** often code for the **same amino acid** (or chemically similar ones).
– If a mutation changes the **third base** (moving horizontally), it often doesn’t change the amino acid at all — this is the **“wobble position.”**
– Example: ACC, ACA, ACG, ACU → all = **Threonine**.
– → Usually **less damaging** (silent mutation).
– If a mutation changes the **first or second base** (jumping vertically into another row), it usually changes the amino acid.
– Example: **ACC → CCC** (Threonine → Proline).
– → Much **more damaging**, because it alters the protein sequence.
– Worst case: if the change lands on a **stop codon** (e.g., ACC → UGA in RNA), translation halts early — a **nonsense mutation**, usually very damaging.
—
👉 So yes:
– **Horizontal (within the same box / third-base changes): usually less damaging.**
– **Vertical (switching rows / first- or second-base changes): usually more damaging.**
Do you want me to diagram this for **ACC specifically**, showing which changes are silent (safe), missense (risky), or nonsense (very damaging)?
See how that is done? Find a pattern and not have to learn all of the digits!
Exactly 👌 — you’ve hit the essence of how biologists (and exam survivors 😅) deal with the codon table: **see the pattern, not memorize all 64 codons**.
Here are the key shortcuts:
1. **Third base = wobble**
– Most of the time, changing the 3rd base (horizontal move) doesn’t change the amino acid.
– → Silent mutation = usually harmless.
2. **First base sets the “family”**
– Codons with the same first letter often give related amino acids.
– Example: G-start codons → Gly, Ala, Asp/Glu, Val (all small or acidic).
3. **Second base determines chemistry**
– U in the 2nd position → hydrophobic amino acids (e.g., Leu, Val, Phe).
– A in the 2nd position → polar or charged amino acids (e.g., Asp, Glu, Lys, Asn).
4. **Stop codons are clustered**
– All involve an A in the second position: UAA, UAG, UGA.
5. **Start codon is unique**
– AUG = Methionine (also the “begin translation” signal).
—
👉 So instead of brute-forcing 64 codes, you only need to remember the **logic grid**:
– 3rd base = wiggle room.
– 2nd base = chemical class.
– 1st base = family anchor.
Would you like me to sketch a **condensed mnemonic codon map** (like a cheat sheet with these patterns baked in)?
Or easier thought – changes in the third amino is not as harmful as the first two
💯 That’s the clean way to think about it.
– **3rd position (the wobble base):**
– Often doesn’t change the amino acid at all → **silent mutation**.
– If it does change, it usually swaps in a chemically similar amino acid.
– → **Least harmful** spot for mutations.
– **1st or 2nd positions:**
– Much more likely to switch to a **different amino acid** (missense).
– Some swaps are conservative (similar chemistry, less bad), others are radical (different charge/shape, very bad).
– 2nd base especially tends to control the **chemical nature** (hydrophobic vs polar vs acidic).
– → **More harmful** when mutated.
– **Special case:** if a mutation makes a **stop codon** early → **nonsense mutation**, almost always very damaging.
👉 So your simplified rule of thumb:
**“Third base changes are usually harmless; first two are usually harmful.”**
Do you want me to translate that into a **one-liner test trick** you can instantly apply on exams?
Astrobiology for the week is done 9.29 starts a new chapter. See you then. Off to C++, see you there!
Got it 👍 — Astrobiology on pause until **9/29**, and we’ll switch gears to **C++** now. I’ll be ready to jump in when you are. 🚀