Unit 10 Topic 3.4 In Our Backyard Flashcards
1
Q
Life demonstrates… (10 things)
A
- Organization and separation from the external environment
- Metabolism
- Homeostasis (maintain a stable internal environment despite changes in the external environment)
- Response to stimuli
- Growth
- Reproduction
- Adaptation (adapting to environmental changes through natural selection.)
- Movement (even some form of movement at the cellular level)
- Excretion (waste products due to metabolic processes.)
- Death
2
Q
What are the three things crucial conditions for life?
A
- The presence of elements that combine into complex macromolecules.
- A solvent
- An energy source that can help drive chemical reactions
3
Q
Elements that combine into complex macromolecules.
What are these molecules on earth?
What are the three things crucial conditions for life?
A
- carbon
- hydrogen
- nitrogen
- oxygen
- phosphorus
- sulphur
CHNOPS
4
Q
Elements that combine into complex macromolecules.
What macromolecules does CHNOPS combine into? What does this do?
What are the three things crucial conditions for life?
A
- Combine to form four macromolecules that fulfill cellular operations’ basic functions.
These are (CLAN):
* carbohydrates
* lipids
* amino acids (the building blocks of proteins)
* nucleic acids like DNA and RNA.
5
Q
Elements that combine into complex macromolecules.
What are some other examples of organic building blocks (2)?
What are the three things crucial conditions for life?
A
- On Earth, some were likely produced by reactions in the primitive atmosphere and at hydrothermal vent systems.
- We also noted that a class of meteorites called carbonaceous chondrites are rich in organic molecules.
6
Q
A solvent
What is it? On Earth?
What are the three things crucial conditions for life?
A
- A solvent is a substance into which other substances (solutes) can dissolve.
- On Earth, the universal solvent for life is water
7
Q
A solvent
Polarity of water - how can it dissolve other compounds?
What are the three things crucial conditions for life?
A
- Water has a polar arrangement of (H2O); a positive electrical charge on one side (hydrogen) and a negative charge on the other (oxygen).
- This polarity enables water molecules to attract various types of molecules.
- Water can become so heavily attracted to a different compound, for example, salt (NaCl), that it can disrupt the attractive forces that hold the sodium and chloride in the salt compound together and, thus, dissolve it.
- This allows chemical substances to remain suspended and interact in complex ways in 3D space, increasing the ease with which complex macromolecules can form.
8
Q
An energy source that can help drive chemical reactions
Photosynthesis? WHY/WHY NOT
What are the three things crucial conditions for life?
A
- It was thought the foundation of all ecosystems was energy from the sun, driving photosynthesis.
- While photosynthesis is probably the dominant process, we now know that other ecosystems do not rely on sunlight.
9
Q
An energy source that can help drive chemical reactions
What is it?
What are the three things crucial conditions for life?
A
- Hydrothermal vent systems
- The possibility of life in these deep, dark areas of the oceans where extremely hot, poisonous clouds of minerals are showering the ocean floor was not considered before their discovery.
- Vent ecosystems rely on chemosynthesis, where bacteria and other microorganisms use inorganic substances, such as hydrogen sulphide, to power their metabolisms.
10
Q
What is an Extremophile?
A
life forms that live in particular areas considered “extreme” by human standards
11
Q
Extremophiles in Extreme Temperatures
One of the most well-known categories of extremophiles are…
A
thermophiles, which flourish in high-temperature environments.
12
Q
Where do Thermophiles thrive?
A
- Hydrothermal vents on the ocean floor, where temperatures can exceed 400°C, prevent water from boiling because of the high pressure at depth
- The water temperature falls fairly quickly away from the vents, but thermophile archaea have been found thriving in water at 122°C.
13
Q
Why do Extremophiles thrive at high temperatures?
A
- For most organisms, high temperatures cause proteins to denature (unfold),
- But thermophile proteins fold up very tightly, allowing them to survive in the intense heat of their surroundings.
14
Q
What opposes Thermophiles?
WHY?
A
- Psychrophiles inhabit extremely cold environments like the Arctic and Antarctic (Figure 4-right), where temperatures can plummet below freezing.
- The microbes in this environment produce a kind of cellular antifreeze that presents the development of ice crystals within the cell’s cytoplasm.
- Microbial activity has been found in soils frozen below -39°C.
15
Q
Extremophiles in Extreme pH
What are two examples?
A
- Acidophiles and alkaliphiles are extremophiles that have adapted to highly acidic or alkaline environments
16
Q
Extremophiles in Extreme pH
How do Acidophiles and alkaliphiles adapt?
A
- Occurs when the mineral pyrite (FeS2) reacts with oxygen in the atmosphere, forming sulfuric acid.
17
Q
Extremophiles in Extreme pH
At the other extreme of pH
A
are alkaline lakes that demonstrate high concentrations of compounds like sodium carbonate and contain rich alkaliphile microbial communities
18
Q
Extremophiles in Extreme Salinity
What types/examples?
A
- Halophiles
- Extremophiles that thrive in high-salinity environments, such as salt flats, salt mines, and salt pans
19
Q
Extremophiles in Extreme Salinity
How does it work?
A
- Normally, very salty conditions dehydrate cells with water physically moving out of the cell and into the external environment by osmosis.
- Halophiles produce chemicals that increase the osmotic potential of the cell, preventing water from being drawn out by the salt.
20
Q
”Extreme Extremophiles”
What + examples
A
- Some microbes have demonstrated remarkable resilience to a variety of extreme condition
- Deinococcus radiodurans is a bacterium known for its exceptional resistance to radiation. It can also withstand cold temperatures, dehydration, vacuum and acidic environments.
21
Q
What was discovered about our unique “backyard”?
A
- In the 1970s, robotic probes returned images of planets and moons within our solar system, revealing no signs of Earth-like conditions.
- This led to the prevailing belief that the likelihood of life in our celestial “backyard” was minimal to non-existent.
22
Q
Mars - Early views and exploration
Why is Mars the best chance of finding life? WATER EXPLANATION
A
- The possibility that life and perhaps intelligent life existed on Mars (making it a possible other source of life) was boosted when Dr. Percival Lowell claimed to have found evidence of canals on Mars
- Lowell described Mars as a dying planet desperately trying to move the last vestiges of water from its ice caps over its drying surface in an extensive irrigation project that, in part, inspired HG Wells to write his famous book, the War of the Worlds.
23
Q
Were Lowell’s canals true?
A
- NO - not after a fly-by of Mars, showing a dead planet
- Lowell’s canals were “illusions”
24
Q
The Viking Mission
A
- The Viking mission deposited two landers on the surface armed with a series of biological instruments to detect the presence of life.
- When the landers finally arrived, they returned images of a cold, dry desert planet
NASA - after the fly-by
25
Conditions on Mars Today
| DISTANCE, SIZE, AND SURFACE TEMP VS. EARTH
* Mars = 232 million km away from sun, while Earth = 148 million km away
* Mars diameter = 6,792 km; much smaller than Earth
* The average surface temperature on Mars hovers around -65°C, a stark contrast to Earth's milder 15°C.
26
Conditions on Mars Today
| ATMOSPHERE VS. EARTH
* Mars's atmosphere, comprising about 95% carbon dioxide, is **significantly thinner than Earth’s**, with an **atmospheric pressure at the surface less than 1% of that found on our planet**.
* These low-pressure conditions would cause liquid water to evaporate at the surface rapidly.
* Additionally, **Mars lacks an active magnetosphere**, leading to high levels of radiation at the surface.
27
Evidence of Life on Ancient Mars - Mars in the past
* Likely had a **thicker atmosphere** and a **magnetic field**, which could have helped shield the surface from radiation.
* Evidence suggests that **liquid water once flowed on its surface** and may have even formed **oceans**.
* **Much of that water is now frozen at the poles.** Mars was also more geologically active in the past, as evidenced by its numerous inactive volcanoes and possible tectonic activity
28
Was early mars suitable for life?
* YES
* Early Mars had all the conditions necessary for life to evolve: liquid water, a source of organic materials from meteorites, energy from the sun and perhaps from active volcanic heat sources.
* In addition, all the life-essential "**CHNOPS**” have now been identified on the surface of Mars.
29
How can we find out what happened to Mars?
| What other fossil hints are there?
* **MISS**: Microbially-induced sedimentary structures.
* In addition to stromatolites, microbes can cause **wrinkles** on the surface of sediments called Elephant Skin Textures
* Images taken by the Curiosity Rover on a potentially dried lake that may have undergone seasonal flooding billions of years ago.
* Some of the features on the image resemble MISS fossils from the Precambrian found on Earth today
30
How can we find out what happened to Mars?
to find **biosignatures** or convincing **fossils** that date to this period on Mars
31
Life on Mars Today?
| Is Mars completely uninhabitable?
Although Mars today is very challenging for life, **it still possesses essential life elements (CHNOPS)** and plenty of **water** frozen at the poles or within the Martian regolith, a blanket of unconsolidated loose material covering the rocky surface.
32
Where could liquid water on Mars exist today?
* Liquid water might still occur in the subsurface close to old volcanic centers warm enough to melt the ice.
* The water would be very salty, but halophile Martian microbes might survive in such conditions.
33
Mars - possibility of a subsurface biosphere
* Possibility of a subsurface biosphere comes from analyzing **methane**, a gas commonly produced by microbial activity on Earth.
* The Curiosity Mars rover **discovered that methane appears to have a *seasonal cyclicity in Mars's atmosphere***, with more gas released during the summer months
* Could this be evidence of a subsurface colony of methanogenic (methane-producing) microbes that are more active when the Martian surface warms during the summer?
* It is possible, but it is important to note that rocks rich in the mineral Olivine (common on Mars) can react with liquid water to produce methane (Figure 13-right).
34
At present, several possibilities regarding life on Mars present themselves:
1. Mars evolved a **biosphere that is now completely extinct**
2. Mars' **biosphere still exists but in very restricted locations**
3. **Life never evolved on Mars**
35
Icy Moons
| What are they? What are some examples?
* Icy moons are a class of natural satellites with surfaces mostly composed of ice.
* We will focus on two icy moons: **Jupiter’s Europa** and **Saturn’s Enceladus.**
36
Europa
| Outward traits
The surface of Jupiter’s moon, Europa, exhibits a complex network of ridges and cracks and a notable absence of craters, suggesting a degree of geological activity
37
Europa - tidal flexing -> activity
* As Europa orbits around Jupiter, the gravitational influence induces tidal flexing on the moon, akin to a baker kneading dough.
* This gravitational kneading process is **hypothesized to generate heat within Europa's rocky core**.
* Consequently, **this internal heat is believed to have facilitated the formation of a saline ocean beneath Europa's icy crust. **
* The visible ridges and cracks on the moon's surface indicate dynamic movements within this subsurface ocean.
38
How do Europa's oceans differentiate from other Jovian moons?
* While other moons in the Jovian system, such as Ganymede and Callisto, may also harbour subsurface oceans, **it is thought these are situated between layers of ice**
* In contrast, **Europa's ocean is believed to have *direct contact with its rocky interior***
* This direct interface is of particular interest due to the potential for chemical processes that may produce a variety of substances necessary for the evolution of life
39
Enceladus
* Enceladus, a moon of Saturn, has provided clear evidence of a subsurface liquid ocean below its south pole
* These cracks radiate heat, with temperatures recorded by Cassini at -80°C, 120°C warmer than the rest of the surface (detected amines/amino acids, phosphorous)
* The water was salty, and the composition was very similar to that being released at hydrothermal vents on Earth.
40
What did tidal flexing do to Enceladus and Europa?
* As with Europa, tidal flexing is probably the mechanism that has produced a subsurface liquid ocean in Enceladus.
* It has been suggested that the **heat generated by this process in both moons may be sufficient for the formation of hydrothermal vents on the surface of their rocky cores**, potentially supporting a microbial chemosynthetic ecosystem akin to those found in Earth's oceans
41
Titan - how does it differ?
* Titan, a moon of Saturn, is **the only moon with a thick atmosphere**; 96 % nitrogen, the rest predominantly methane.
* It is also the **only other object with stable bodies of liquid on its surface**.
* In Titan's case, **this liquid is methane (CH4) and Ethane (C2H6), gasses on Earth but liquids in the extreme cold (around -179°C) on Titan**.
* Hydrocarbons cycle through Titan, similar to how water cycles on Earth. Methane is evaporated from the moon's surface, forming clouds that generate liquid methane rain that returns to the lakes in methane river systems.
