1
Q
What causes freezing to be harmful to organisms?
A
Ice crystals damage cells and tissues, dehydration due to extracellular freezing, and oxidative stress during metabolic arrest.
2
Q
What are the two main strategies for surviving extreme cold?
A
Freeze avoidance and freeze tolerance.
3
Q
How do freeze-avoiding animals prevent ice formation?
A
They use supercooling, antifreeze proteins, desiccation, and behavioral strategies.
4
Q
Give examples of freeze-avoiding organisms.
A
Beetles and notothenioid fish.
5
Q
What is freeze tolerance?
A
A strategy allowing controlled ice formation within the body using cryoprotectants like glucose and glycerol.
6
Q
Name some freeze-tolerant species.
A
Amur sleeper and Siberian salamander.
7
Q
How do arthropods survive freezing conditions?
A
They combine supercooling and extracellular freezing, with post-transcriptional modifications (gall fly) or stage-dependent survival (leaf beetles).
8
Q
How do intertidal aquatic invertebrates cope with freezing?
A
They use aquaporins, ice-binding proteins, and heat shock proteins (e.g., mussels).
9
Q
How do Antarctic fish avoid freezing?
A
They produce antifreeze glycoproteins.
10
Q
How do wood frogs survive freezing?
A
They accumulate glucose and urea and regulate microRNAs and membrane adaptations.
11
Q
How do Siberian salamanders tolerate freezing?
A
They rely on anaerobic glycolysis and glycerol accumulation.
12
Q
Why is Rana sylvatica notable?
A
It can survive up to 65% body water freezing and increases glucose, urea, and microRNA levels.
13
Q
Why are studies of freeze tolerance important?
A
They have implications for cryopreservation, biomedical uses, conservation, and understanding climate resilience.
14
Q
What do all prokaryotes have in common?
A
They lack a nucleus and membrane-bound organelles.
15
Q
Are prokaryotes unicellular or multicellular?
A
Most are unicellular, but some form colonies or filaments (e.g., cyanobacteria).
16
Q
What is the most accurate strategy for identifying and classifying prokaryotes?
A
DNA/RNA analysis.
17
Q
Why is horizontal gene transfer a challenge for classification?
A
It moves genes between unrelated organisms, making evolutionary relationships hard to trace.
18
Q
Which molecule is used to classify Bacteria and Archaea into different domains?
A
Ribosomal RNA (rRNA).
19
Q
How do bacteria and archaea differ in their cell membranes?
A
Bacteria have ester-linked phospholipids; archaea have ether-linked phospholipids.
20
Q
What type of cell wall do bacteria have that archaea lack?
A
Peptidoglycan cell walls.
21
Q
Which type of bacteria stains purple in the Gram stain?
A
Gram-positive bacteria.
22
Q
Why do gram-positive bacteria stain purple?
A
They have thick peptidoglycan walls that retain the crystal violet dye.
23
Q
Why do gram-negative bacteria stain pink?
A
They have thin peptidoglycan layers and an outer membrane that prevents crystal violet retention.
24
Q
Why are gram-negative bacteria often harder to treat?
A
Their outer membrane is toxic and resistant to antibiotics and immune responses.
25
What are the three main bacterial shapes?
Cocci (round), bacilli (rods), and spirilli (spiral-shaped).
26
What is metabolism?
Life-sustaining chemical reactions that generate energy, build molecules, and remove waste.
27
What are the two categories of organisms based on carbon source?
Autotrophs (fix CO2) and heterotrophs (use organic carbon).
28
What are phototrophs?
Organisms that obtain energy from light.
29
What are chemotrophs?
Organisms that obtain energy from the oxidation of chemical compounds.
30
What are chemo-organo-heterotrophs?
They use organic molecules for both energy and carbon (e.g., most bacteria, animals, fungi).
31
What are chemo-litho-heterotrophs?
They use inorganic molecules for energy and organic molecules for carbon (e.g., sulfur-oxidizing bacteria).
32
What are chemoautotrophs?
They use inorganic molecules (H₂, H₂S, NH₃) for energy and CO₂ for carbon (e.g., methanogens).
33
What are photoheterotrophs?
They use light for energy and organic compounds for carbon (e.g., halobacteria).
34
What are photoautotrophs?
They use light for energy and CO₂ for carbon (e.g., cyanobacteria).
35
What do photoautotrophs produce as a byproduct?
Oxygen.
36
Why is metabolic type not a reliable way to classify prokaryotes?
Because many unrelated species share similar metabolic strategies.
37
Why are protists no longer considered a kingdom?
Because they are a paraphyletic group with members more closely related to other eukaryotes than to each other.
38
What do all protists have in common?
All are eukaryotes, mostly unicellular, can reproduce sexually, and live in moist environments or symbiotic relationships.
39
How do protists perform complex functions while unicellular?
They have specialized organelles like nuclei, vacuoles, cilia, and pellicles that perform different tasks.
40
Which metabolic process can eukaryotes not utilize?
Chemoautotrophy.
41
How did photosynthesizing eukaryotes evolve?
A heterotrophic eukaryote formed an endosymbiotic relationship with a cyanobacterium, which became a chloroplast.
42
What evidence supports the endosymbiotic origin of chloroplasts?
Chloroplasts have circular DNA, bacterial-like ribosomes, and double membranes similar to cyanobacteria.
43
What pigments are found in red and green algae?
Red algae: chlorophyll a and phycoerythrin; Green algae: chlorophyll a and b.
44
What is secondary endosymbiosis?
When a non-photosynthetic eukaryote engulfs a photosynthetic eukaryote, leading to new photosynthetic lineages.
45
Example of a mixotrophic protist?
Euglena – can photosynthesize and feed on organic molecules.
46
How does Paramecium bursaria obtain chloroplasts?
By forming mutualistic relationships with green algae; chloroplasts are not inherited but acquired from the environment.
47
What disease does Giardia intestinalis cause?
Beaver fever (giardiasis).
48
What pigments are in brown algae?
Chlorophyll a, c1, c2, and fucoxanthin.
49
What causes red tide?
Harmful algal blooms from dinoflagellates that can produce toxins causing paralytic shellfish poisoning.
50
What is bioluminescence in dinoflagellates?
Light emission when stressed or agitated.
51
What protist causes malaria?
Plasmodium (supergroup Chromalveolata).
52
What are slime molds?
Slime molds are a diverse group of organisms within the Protista kingdom, though they share characteristics with fungi
53
What material do Forams use to make shells?
Calcium carbonate.
54
What material do Radiolaria use for shells?
Silica.
55
How are some cercozoans photosynthetic?
Through secondary symbiosis with green algae.
56
How is Paulinella photosynthetic?
Through primary symbiosis with cyanobacteria.
57
Why do algae have different pigments?
To absorb different wavelengths of light and occupy various depths — resource partitioning.
58
How many times did multicellularity evolve?
At least 25 times independently.
59
Which eukaryotic groups evolved complex multicellularity?
Animals, fungi, brown algae, red algae, green algae, and plants.
60
What are the advantages of multicellularity?
Larger size, longer lifespan, and cell specialization for complex functions.
61
Is multicellularity always advantageous?
Not necessarily — most organisms remain unicellular; multicellularity mainly enables larger size.
62
What can DNA analysis be used for in evolutionary biology?
It can confirm evolutionary relationships among organisms by comparing specific DNA sequences, such as the COI gene.
63
What is a phylogenetic tree?
A diagram that shows the evolutionary relationships among organisms based on similarities and differences in genetic or physical traits.
64
What type of information can be used to build a phylogenetic tree?
Body shape, habitat, and function of forearms can all provide clues to evolutionary relationships.
65
Which species form a sister taxon with the walrus?
Based on DNA evidence, the killer whale is more closely related to the walrus than other species.
66
Why might species with similar appearances not be closely related?
Because of convergent evolution — similar traits evolve independently in unrelated lineages due to similar environmental pressures.
67
What is convergent evolution?
The independent evolution of similar traits in different species due to adaptation to similar environments or ecological niches.
68
What are analogous structures?
Structures that have similar functions but evolved independently and do not share a common ancestral origin (e.g. flippers in whales, manatees, and walruses).
69
What is divergent evolution?
The process by which two or more related species become more dissimilar over time, often leading to the formation of new species.
70
What are homologous structures?
Structures that are similar because they were inherited from a common ancestor, even if they serve different functions (e.g. forelimb bones in whales, elephants, and bears).
71
How does DNA sequence analysis improve accuracy in determining evolutionary relationships?
It provides objective molecular data that can reveal relationships not evident from morphology alone.
72
Why do species like killer whales, walruses, and manatees have similar body shapes?
Because of convergent evolution — they live in similar aquatic environments where streamlined bodies and flippers are advantageous.
73
What gene is often used in DNA analysis for identifying evolutionary relationships?
The cytochrome oxidase subunit I (COI) gene.
74
What organisms are fungi most closely related to?
Fungi are most closely related to nucleariid protists.
75
What are nucleariids?
Unicellular, mainly aquatic amoebas that lack cell walls and use pseudopodia for movement and feeding.
76
What is the fungal cell wall made of?
Chitin, unlike plant cell walls which are made of cellulose.
77
How do fungi store carbohydrates?
As glycogen, similar to animals.
78
What type of nutrition do fungi have?
Fungi are chemoheterotrophs that perform extracellular digestion (osmotrophy).
79
What is osmotrophy?
Feeding by secreting exoenzymes to digest food externally, then absorbing nutrients.
80
How does fungal digestion differ from nucleariid digestion?
Fungi digest food extracellularly, while nucleariids use intracellular digestion through phagocytosis.
81
What are saprotrophs?
Fungi that obtain carbon by breaking down dead organic matter.
82
What are parasitic fungi?
Fungi that obtain nutrients from living hosts, often causing disease (e.g., chytrid fungus in amphibians, Dutch elm disease).
83
What is the difference between osmotrophy and saprotrophy?
Osmotrophy describes how fungi feed, while saprotrophy describes what they feed on (dead matter).
84
How do fungi reproduce?
Through spores, either sexually or asexually.
85
What are spores?
Reproductive cells used for dispersal and survival in harsh environments.
86
When do zygomycetes reproduce sexually?
When environmental conditions are unfavorable or changing.
87
What protects zygosporangia?
A thick wall containing chitin and melanin to resist desiccation, UV, and temperature extremes.
88
Which fungal phylum reproduces mostly sexually?
Basidiomycota.
89
Do fungi produce eggs and sperm?
No, fungi do not produce eggs or sperm in the same way as animals. Instead of separate sexes, most fungi have different mating types, and **their sexual reproduction involves the fusion of two haploid nuclei from compatible hyphae (filamentous structures).**
90
What are monokaryotic and dikaryotic hyphae?
Monokaryotic hyphae have one haploid nucleus per cell; dikaryotic hyphae have two haploid nuclei per cell.
91
What are the main fungal phyla?
Chytridiomycota, Blastocladiomycota, Zygomycota, Glomeromycota, Ascomycota, and Basidiomycota.
92
What are the key features of Chytridiomycota?
Mostly unicellular, aquatic, have chitin walls, flagellated spores, and perform extracellular digestion.
93
What makes Blastocladiomycota unique?
They exhibit alternation of generations with flagellated spores and gametes.
94
What are the features of Zygomycota?
Multicellular molds with coenocytic (aseptate) hyphae, mostly asexual, haploid-dominated, and terrestrial.
95
What are the features of Glomeromycota?
Multicellular fungi with aseptate hyphae that reproduce asexually and form arbuscular endomycorrhizas with plant roots.
96
What are the characteristics of Ascomycota?
Mostly multicellular with septate hyphae, reproduce mainly asexually via conidia, and form lichens and ectomycorrhizas.
97
What are the characteristics of Basidiomycota?
Mostly multicellular with septate, dikaryotic hyphae; reproduce sexually via basidiocarps; form ectomycorrhizas.
98
How is fungal classification changing?
DNA evidence shows traditional morphology-based classifications are not phylogenetically accurate.
99
What is lichen?
A mutualistic relationship between **fungi (Ascomycota) and algae or cyanobacteria.**
100
How does the fungus benefit in a lichen?
It receives glucose from the algae or cyanobacteria.
101
How does the algae or cyanobacteria benefit in a lichen?
They receive moisture and protection from the fungus.
102
How do fungi facilitate plant colonization on land?
Through mutualisms like lichens and mycorrhizas that increase soil formation and nutrient uptake.
103
What are mycorrhizas?
Mutualistic relationships between fungi and plant roots that enhance water and nutrient absorption.
104
How do fungi contribute to soil formation?
By breaking down rocks, releasing acids, and decomposing organic matter to form mineral-rich soil.
105
What is the closest living relative to animals?
Choanoflagellates, a group of single-celled protists that share similarities with sponge choanocytes.
106
When did the first animals evolve?
Around 700 million years ago, and they were strictly marine.
107
How do all animals obtain energy and carbon?
All animals are chemoheterotrophs — they get both energy and carbon from organic molecules.
108
What are the main feeding strategies in animals?
-Filter feeders
-carnivores
-herbivores
-omnivores
-and parasites.
109
Which characteristics are shared by all animals?
All animals are multicellular and have differentiated cells.
110
What are the main characteristics used to classify animals?
-Body symmetry
-Hox genes
-tissue specialization
-germ layers
-embryonic development
-and presence of a notochord.
111
Why are sponges and comb jellies considered basal taxa?
They lack true tissues and Hox genes.
112
What are Hox genes?
Genes that regulate embryo development and determine the body plan and structure of different regions.
113
What happens if a Hox gene mutates?
It can alter the number or arrangement of body parts, such as extra limbs or misplaced organs.
114
What are the main types of body symmetry in animals?
- Asymmetrical
- radial
- rotational
- bilateral symmetry.
115
Which animal phyla have no true tissues?
Sponges (Porifera) and comb jellies (Ctenophora).
116
What are germ layers?
Ectoderm, mesoderm, and endoderm — layers in the embryo that give rise to specialized tissues and organs.
117
Which animals are diploblastic?
Cnidarians and ctenophores — they develop two germ layers (ectoderm and endoderm).
118
Which animals are triploblastic?
All bilateral animals — they develop three germ layers (ectoderm, mesoderm, and endoderm).
119
What is the difference between protostomes and deuterostomes?
Protostomes form the mouth first; deuterostomes form the anus first.
120
What type of cleavage do protostomes have?
Spiral cleavage — quick but determinate; cell fates are fixed early.
121
What type of cleavage do deuterostomes have?
Radial cleavage — slower but indeterminate, allowing flexible cell development.
122
What is the advantage of deuterostome development?
It allows more complex body plans and larger animals due to indeterminate cleavage.
123
What is cephalization?
The development of a head with sensory organs and a brain — associated with bilateral symmetry and mobility.
124
Which animal phyla show high degrees of cephalization?
Arthropods, mollusks (especially cephalopods), and annelids.
125
Why do animals with bilateral symmetry often have high mobility?
Bilateral symmetry and cephalization help coordinate movement and sensing prey/predators in front of the body.
126
Why are animals with radial symmetry suited for sessile lifestyles?
They can sense stimuli and capture food from all directions, ideal for aquatic or stationary life.
127
What are examples of asexual reproduction in animals?
Budding (e.g. Hydra), fragmentation (e.g. flatworms, sponges), and parthenogenesis (e.g. geckos).
128
What is parthenogenesis?
A form of asexual reproduction where females produce diploid eggs without fertilization.
129
When did animal diversity increase drastically?
During the Cambrian explosion about 540 million years ago.
130
What factors contributed to the Cambrian explosion?
Genome duplication, rise of Hox genes, predator-prey coevolution, increased oxygen, calcium availability, and new habitats.
131
What caused the increase in oxygen around 650 million years ago?
The evolution of photosynthesizing eukaryotes — algae and early plants.
132
Which group evolved during the Cambrian diversification?
Chordates and early vertebrates.
133
What are the key characteristics of all chordates?
All chordates have a notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail, and endostyle (which becomes the thyroid in many species).
134
What is the function of the notochord?
It provides structural support and serves as a site for muscle attachment during swimming.
135
What does the dorsal hollow nerve cord develop into?
It develops into the brain and spinal cord in most chordates.
136
What is the function of the post-anal tail?
It aids in locomotion in aquatic species and balance in terrestrial species.
137
What is the function of pharyngeal slits?
They allow filter feeding in some species and develop into gills in others.
138
What is the function of the endostyle?
It assists in filter feeding but develops into the thyroid gland in many chordates.
139
Why are tunicates considered chordates?
Their larvae possess all chordate features, though adults retain only pharyngeal slits.
140
What facilitated the evolution of chordates?
Genome duplications (including Hox genes) allowed for more complex body plans and functions.
141
What benefits did the vertebral column provide?
It protected the nerve cord, allowed for efficient movement, and supported the body.
142
What was the evolutionary advantage of jaws?
They enabled chordates to capture and tear food, making them more efficient predators.
143
What was the evolutionary benefit of lungs?
They allowed efficient gas exchange, enabling survival in oxygen-poor water and on land.
144
What did lungs evolve into in ray-finned fishes?
They evolved into the swim bladder for buoyancy control.
145
What was the evolutionary significance of lobe fins?
They evolved into limbs, allowing animals to move and exploit resources on land.
146
What are the benefits of the amniotic egg?
It protects against dehydration, allows gas exchange, stores nutrients, and cushions the embryo.
147
What adaptation allowed reptiles to lay eggs on land?
The amniotic egg, which eliminated the need for a larval stage.
148
What structures evolved from keratin?
Scales, claws, hair, and feathers.
149
What are the benefits of scales, hair, and feathers?
They conserve water and heat, provide protection, and aid in camouflage.
150
What are adaptations?
Beneficial traits that increase survival and reproduction, becoming more common in a population over generations.
151
How do adaptations evolve?
Through natural selection—traits that improve survival and reproduction become more common over time.
152
What are examples of chordate adaptations to cold?
Fur, feathers, blubber, and countercurrent heat exchange systems in birds and mammals.
153
What makes mammals unique among chordates?
They nurse young with milk, have hair or blubber, give live birth (mostly), are endothermic, and have kidneys for water conservation.
154
What is the main advantage of endothermy?
It allows animals to maintain a stable internal temperature and stay active in cold environments.
155
Which structures protect mammals from temperature extremes?
Hair, fur, and blubber layers beneath the skin.
156
What is the primary function of the vertebral column?
To protect the dorsal nerve cord and support movement.
157
Which genetic change was crucial for chordate evolution?
Multiple genome duplications, including duplication of Hox genes, enabling complex development.
158
What do all photosynthetic eukaryotes have in common?
They contain chlorophyll a and share a photosynthetic common ancestor.
159
What is contained in The Archaeplastida supergroup?
- red algae
- chlorophytes
- charophytes
- land plants
160
Which group forms the basal taxon of Archaeplastida?
Red algae (Rhodophyta).
161
Why do red algae appear red?
They contain phycoerythrin and phycocyanin pigments, not chlorophyll b.
162
Do green algae form a clade?
Yes, because chlorophytes and charophytes share a common ancestor and are monophyletic.
163
How do chlorophytes differ from charophytes?
Chlorophytes are mostly unicellular or simple multicellular and lack plasmodesmata; charophytes are complex, multicellular, and have plasmodesmata.
164
What are plasmodesmata?
Channels between plant cells that allow efficient communication and coordination.
165
What environmental challenges did early land plants face?
Desiccation, UV radiation, and the need for structural support and gas exchange.
166
What were the key adaptations that allowed plants to live on land?
Protected spores, cuticle, stomata, vascular tissue, roots, pollen, seeds, and flowers.
167
What are protected spores and their function?
Spores surrounded by sporopollenin; they resist desiccation and UV damage.
168
What does 'alternation of generations' mean in plants?
Plants alternate between a multicellular haploid gametophyte and a multicellular diploid sporophyte stage.
169
What is the primary difference between sporophyte and gametophyte stages?
The sporophyte produces spores via meiosis, while the gametophyte produces gametes via mitosis.
170
How does the plant life cycle differ from that of animals?
Plants have two multicellular stages (gametophyte and sporophyte), while animals have one multicellular stage (diploid).
171
What is the function of the cuticle?
A waxy layer that prevents water loss, protects from UV radiation, and deters pathogens.
172
What is the function of stomata and guard cells?
Stomata allow gas exchange; guard cells regulate their opening and closing to balance CO₂ intake and water loss.
173
Which plants lack a cuticle and stomata?
Liverworts.
174
Why are non-vascular plants found in moist environments?
They lack roots and vascular tissue, requiring water for reproduction and nutrient transport.
175
What is desiccation tolerance in bryophytes?
The ability to survive long periods without water by entering dormancy.
176
What structures make vascular plants more efficient?
- Xylem
- phloem
- true roots
- lignin (for support and water transport.)
177
What is the main difference between bryophytes and ferns?
Bryophytes have a dominant gametophyte and no vascular tissue; ferns have a dominant sporophyte and vascular tissue.
178
What do xylem and phloem transport?
Xylem transports water and minerals; phloem transports sugars and proteins.
179
What is a mycorrhiza?
A mutualistic relationship between fungi and plant roots that improves water and nutrient absorption.
180
What is unique about spike moss (Selaginella)?
It is heterosporous—produces microspores and megaspores—and has a reduced gametophyte.
181
When did seed plants first appear?
About 400 million years ago, becoming dominant around 300 million years ago.
182
Why did gymnosperms become dominant 300 million years ago?
They were adapted to cold, dry climates with seeds and pollen resistant to desiccation.
183
What are the benefits of seeds?
Protection, dormancy, nutrient storage, and improved dispersal.
184
What are the benefits of pollen?
Protection from desiccation and independence from water for fertilization.
185
Where is the male gametophyte found in seed plants?
Inside the pollen grain.
186
What is the function of the female cone (ovule cone)?
It houses the megaspore and female gametophyte, which produces the egg.
187
How are conifers adapted to cold environments?
They have needle-like leaves, thick cuticles, antifreeze compounds, and flexible branches to shed snow.
188
What hypothesis about gymnosperm evolution is currently supported?
The Anthophyte hypothesis—gymnosperms form a paraphyletic group, with angiosperms derived from them.
189
What is Biology?
The scientific study of life and living organisms — asking and answering questions about how life works and evolves.
190
What are the basic requirements for life?
- Water
- energy sources
- C, H, O, N, P, S.
191
Why is water essential for life?
It acts as a solvent, allows biochemical reactions, helps transport substances, regulates temperature, provides structure, and protects organs.
192
What property makes water a good solvent?
Its polarity allows it to dissolve polar and charged molecules.
193
Why does water have a high specific heat capacity?
Because of hydrogen bonding, which makes it take a lot of energy to change its temperature.
194
How does water’s high heat capacity benefit life on Earth?
It stabilizes Earth's climate and helps organisms regulate their internal temperature.
195
Why is ice less dense than water?
Hydrogen bonds keep water molecules further apart in ice, allowing ice to float.
196
What is turgor pressure and why is it important?
Turgor pressure is the pressure of water inside plant cells that maintains structure and support.
197
What are the main energy sources for life?
- Light (photosynthesis)
- chemical oxidation (chemosynthesis).
198
What are photoautotrophs?
Organisms that use sunlight to fix carbon and produce energy-rich molecules.
199
What are chemoautotrophs?
Organisms that use energy from inorganic molecules to fix carbon, often living near hydrothermal vents.
200
What are the four major macromolecules of life?
- Carbohydrates
- lipids
- proteins
- nucleic acids (DNA/RNA).
201
What elements are most important for forming organic molecules?
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur (CHONPS).
202
What are the characteristics of living organisms?
- Organization
- response to environment
- reproduction
- homeostasis
- metabolism
- evolution.
203
Which characteristics are unique to living organisms?
Reproduction and evolution.
204
What structure allows organisms to maintain homeostasis and metabolize?
The cell membrane.
205
Why is the cell membrane essential for life?
It controls what enters and exits the cell, maintains internal conditions, and enables cell communication.
206
What does it mean that water molecules are polar?
They have a slightly negative oxygen end and a slightly positive hydrogen end due to unequal electron sharing.
207
What kind of bonds form between water molecules?
Hydrogen bonds.
208
How does evaporation of water cool the body?
Evaporation requires energy, removing heat from the body in the process.
209
Why is biology a constantly changing science?
Because new observations and discoveries update our understanding of life.
210
What are viruses made of?
A nucleic acid (DNA or RNA) enclosed in a protein coat called a capsid; some also have a lipid envelope.
211
Are viruses living organisms?
No, because they cannot reproduce or carry out metabolism without a host cell.
212
Why don’t antibiotics work against viruses?
Viruses lack cell walls, membranes, ribosomes, and metabolism — the targets of antibiotics.
213
How do antibiotics kill bacteria?
By disrupting cell walls, membranes, ribosomes, or metabolic enzymes.
214
What mission was launched to study the potential for life on Europa?
NASA’s Europa Clipper mission, launched in 2024 to study Jupiter’s moon Europa for signs of life.
215
What would scientists look for when searching for life on other planets?
Presence of water, energy sources, and organic molecules.
216
What does metabolism mean?
The set of chemical reactions that provide energy and build molecules necessary for life.
217
What is homeostasis?
The ability of an organism to maintain a stable internal environment despite external changes.
218
What are the three main requirements for life?
Liquid water, a source of energy, and biogenic elements (C, O, H, N, P, S).
219
Why is carbon the major component of living organisms?
Because carbon can form four covalent bonds, allowing it to create **complex and stable molecules like proteins, lipids, and nucleic acids.**
220
What are the key biogenic elements essential for life?
Carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur.
221
What are the possible steps that led to life on Earth?
Formation of small organic molecules → large organic molecules → self-replicating molecules → cell membranes → protocells → living cells.
222
What is chemical evolution?
The process by which simple molecules underwent reactions, driven by energy sources like heat, lightning, or radiation, to form complex organic molecules.
223
What evidence suggests that organic molecules can form naturally in the universe?
Comets and asteroids contain thousands of organic compounds, including amino acids.
224
What were the possible sources of energy driving chemical evolution?
Lightning, UV radiation, volcanic heat, and hydrothermal vents.
225
What are amino acids and nucleotides examples of?
Small organic molecules that were precursors to larger macromolecules like proteins and nucleic acids.
226
What is RNA and why is it important to the origin of life?
RNA is a single-stranded nucleic acid that can store information and catalyze reactions, possibly serving as the first genetic and catalytic molecule.
227
What are ribozymes?
RNA molecules that can act like enzymes to catalyze chemical reactions.
228
Why is RNA thought to have formed before DNA?
RNA can both store genetic information and catalyze its own replication, whereas DNA requires proteins for replication.
229
How are RNA nucleotides related to ATP?
RNA nucleotides are structurally similar to ATP, which provides energy in modern cells.
230
What are protocells?
Simple, membrane-bound structures formed from phospholipids that could encapsulate molecules and maintain internal conditions. **Thought to be a precursor to true cells**
231
How could protocells have formed spontaneously?
Protocells could have formed spontaneously through the self-assembly of lipid molecules into a membrane-bound vesicle that encapsulates genetic material like RNA
232
Why were cell membranes essential for life to occur?
They allowed compartmentalization, protection, and the maintenance of stable internal environments for chemical reactions.
233
What is the earliest fossil evidence of life?
Fossilized microbial mats (stromatolites) about 3.5 billion years old.
234
What types of evidence are used to study the origin of life?
Geochemical, fossil, and genetic evidence.
235
What is geochemical evidence for early life?
Isotopic ratios of light carbon (12C) indicating biological activity.
236
What is an isotope?
Atoms of the same element with different numbers of neutrons, giving them different masses.
237
What does isotopic evidence suggest about early life?
Living organisms preferentially used lighter carbon isotopes (12C) to build organic matter.
238
What is LUCA?
The Last Universal Common Ancestor — the most recent organism from which all current life descended.
239
Was LUCA the first living organism?
No, LUCA coexisted with many other primitive extinct cells and was not the very first life form.
240
What did LUCA look like?
It was a single-celled organism with a cell membrane, cell wall, circular DNA, and no nucleus or organelles.
241
Where did LUCA likely live?
Near hydrothermal vents on the ocean floor in an oxygen-free environment.
242
How did LUCA obtain energy?
By oxidizing inorganic compounds like hydrogen (H₂) and hydrogen sulfide (H₂S).
243
What was LUCA’s carbon source?
It fixed carbon from carbon dioxide (CO₂).
244
What genetic material did LUCA have?
A circular DNA chromosome, similar to modern prokaryotes.
245
What does genetic evidence reveal about LUCA?
It shared genes from both bacteria and archaea, suggesting horizontal gene transfer.
246
What do hydrothermal vents provide that could support life?
Heat, minerals, and a steady source of chemical energy for chemosynthetic organisms.
247
What does the phrase 'Perhaps there was never ONE LUCA' mean?
Early life may have arisen in multiple lineages that exchanged genetic material before one lineage survived.
248
What is the purpose of a phylogenetic tree?
To illustrate possible evolutionary relationships among organisms and represent hypotheses about their ancestry.
249
What can phylogenetic trees be used for?
- visualize evolutionary relationships
- test classification hypotheses
- analyze the evolutionary history of organisms.
250
What do the nodes on a phylogenetic tree represent?
Common ancestors shared by descendant lineages.
251
What do the branches on a phylogenetic tree represent?
Evolutionary lineages that diverged from a common ancestor.
252
What do the tips of a phylogenetic tree represent?
Current or extinct species or taxa being compared.
253
Are phylogenetic trees hypotheses or facts?
They are hypotheses that can be supported or rejected through additional research.
254
What did Carolus Linnaeus contribute to taxonomy?
He developed the binomial nomenclature and classified organisms into two kingdoms: Animals and Plants (1758).
255
Who introduced the third kingdom, Protista?
Ernst Haeckel in 1866.
256
Who first distinguished between prokaryotes and eukaryotes?
Édouard Chatton in 1937, proposing the Two Empires system: Prokaryota and Eukaryota.
257
Who proposed the Four Kingdom classification?
Herbert Copeland in 1938, adding Monera as a separate kingdom for prokaryotes.
258
Who proposed the Five Kingdom classification system?
Robert Whittaker in 1969: Monera, Protista, Fungi, Plantae, and Animalia.
259
Who proposed the Three Domain system?
Carl Woese in 1977, later refined in 1990 — Bacteria, Archaea, and Eukarya — based on genetic evidence (rRNA analysis).
260
What are the three domains of life in Carl Woese’s system?
Bacteria, Archaea, and Eukarya.
261
What classification system followed the Three Domains model?
The Two Domains hypothesis (Bacteria and Archaea), where Eukaryotes are thought to have evolved from Archaea.
262
Who proposed the Two Domain hypothesis?
Ford Doolittle, Tom Williams, and others in 2017.
263
What is the main difference between the Five Kingdoms and the Three Domains models?
The Five Kingdoms are based on morphology and physiology; the Three Domains are based on genetic evidence.
264
What is the ‘Web of Life’ concept?
A model suggesting extensive horizontal gene transfer among species, making evolutionary relationships more network-like.
265
What is the ‘Ring of Life’ hypothesis?
A model suggesting that eukaryotes arose from a fusion between bacterial and archaeal lineages.
266
What is a ‘clade’?
A group of organisms that includes a common ancestor and all its descendants.
267
What is the difference between a rooted and an unrooted phylogenetic tree?
A rooted tree shows a common ancestor; an unrooted tree only shows relationships without a specific origin point.
268
Why are phylogenetic trees important in biology?
They help scientists trace evolutionary pathways, classify organisms, and understand the origin of traits.
269
Which classification systems were based primarily on morphology?
Linnaeus’s Two Kingdom and Whittaker’s Five Kingdom systems.
270
Which classification systems were based on molecular or genetic data?
Woese’s Three Domain and Doolittle’s Two Domain systems.
271
What do horizontal gene transfer and endosymbiosis suggest about evolution?
That evolution is not purely linear — genes can move between unrelated lineages, influencing the Tree of Life.
272
What is the purpose of a phylogenetic tree?
To illustrate possible evolutionary relationships among organisms.
273
Do diagonal and vertical phylogenetic trees show the same relationships?
Yes, as long as the order of groups from the root remains the same.
274
What happens if the order of organismal groups changes from the root of the tree?
The interpretation of the phylogenetic relationships changes.
275
What is a taxon?
A group of organisms classified together, such as a kingdom, phylum, or genus.
276
What is taxonomy?
The classification of organisms into groups (taxa) based on shared characteristics or evolutionary relationships.
277
What is a monophyletic group (clade)?
A group that includes a common ancestor and all its descendants.
278
What is a paraphyletic group?
A group that includes a common ancestor but not all of its descendants.
279
Why should taxa form monophyletic groups?
Because modern classifications aim to reflect evolutionary relationships accurately.
280
What happens when a taxon is found to be paraphyletic?
It is reclassified to better reflect evolutionary relationships.
281
Why is 'Monera' considered a paraphyletic group?
Because it excludes eukaryotes, even though they share a common ancestor with bacteria and archaea.
282
Why are protists considered a paraphyletic group?
Because the common ancestor of protists is also the ancestor of plants, fungi, and animals.
283
Why is 'Reptiles' a paraphyletic group?
Because it excludes birds, which share a common ancestor with reptiles.
284
What is a clade?
A monophyletic group that includes an ancestor and all its descendants.
285
What are sister taxa?
Two species or groups that share an immediate common ancestor and are each other’s closest relatives.
286
What is a basal taxon?
The earliest diverging lineage within a phylogenetic tree; it represents the most ancestral group.
287
How can we build a phylogenetic tree?
By identifying characteristics shared among organisms and determining the order in which they evolved.
288
What does a characteristic matrix show?
Which species possess specific traits used to infer evolutionary relationships.
289
What characteristic did all animals in the example share?
Bilateral body symmetry — likely present in the common ancestor.
290
Why are snails considered a basal taxon in the example?
Because they share only bilateral symmetry and diverged before other traits evolved.
291
What are some examples of traits used to classify animals in the example?
Bilateral symmetry, vertebral column, four legs, and fur.
292
What is the problem with building phylogenetic trees based only on physical traits?
Physical similarities may result from convergent evolution (analogous traits) rather than shared ancestry.
293
What is an analogous structure?
A structure that evolved independently in different species but performs a similar function.
294
What is a homologous structure?
A structure inherited from a common ancestor, even if it serves a different function.
295
Why can physical traits be misleading in phylogenetic analysis?
Because they can be influenced by environmental factors rather than genetics.
296
How do modern phylogenetic trees improve accuracy?
They incorporate molecular and genetic data in addition to morphological traits.
297
What is binary fission?
A form of asexual reproduction in which a cell divides into two genetically identical cells.
298
How does binary fission occur in prokaryotes?
The circular DNA replicates, attaches to the cell membrane, and the cell divides by cytokinesis into two identical daughter cells.
299
Does prokaryotic binary fission involve mitosis?
No, because prokaryotes lack a nucleus and only have one circular chromosome, so mitosis is unnecessary.
300
How does binary fission occur in unicellular protists like Paramecium?
DNA replication occurs within the nucleus, followed by mitosis and cytokinesis, producing two genetically identical daughter cells.
301
Why did mitosis evolve in eukaryotes?
Because eukaryotic cells have multiple linear chromosomes that require organization and equal distribution during cell division.
302
What is the main difference between binary fission in prokaryotes and eukaryotes?
Prokaryotic binary fission is simpler and does not involve mitosis, while eukaryotic binary fission includes mitosis to manage multiple chromosomes.
303
What is conjugation?
A process where two cells exchange genetic material through direct contact or a bridge-like connection.
304
How does conjugation occur in prokaryotes?
A donor cell transfers plasmid DNA to a recipient cell through a pilus (sex pilus).
305
Does prokaryotic conjugation produce offspring?
No, it does not produce new cells, only exchanges genetic material for variation.
306
How does conjugation occur in protists such as Paramecium?
Two cells align side by side, exchange micronuclei through a cytoplasmic bridge, then separate and undergo binary fission to reproduce.
307
What is the purpose of conjugation in Paramecium?
To increase genetic variation through recombination, even though no new individuals are produced immediately.
308
What is the main difference between conjugation in prokaryotes and protists?
Prokaryotic conjugation transfers plasmid DNA without reproduction, while protist conjugation involves exchange of nuclear material followed by reproduction.
309
How are binary fission and conjugation different?
Binary fission is asexual reproduction producing identical cells; conjugation exchanges genetic material for diversity but does not create new cells directly.
310
Why are angiosperms considered the most successful plant group?
They represent 90% of all plant species, with about 300,000 species, due to adaptations like flowers, fruits, vascular tissue, and co-evolution with pollinators.
311
What characteristics make angiosperms successful?
Large broad leaves, short life cycle, advanced vascular tissue, flowers, and fruits (protected seeds).
312
How do broad leaves contribute to angiosperm success?
They absorb more light, enable efficient photosynthesis, and support high growth rates and gas exchange.
313
Why is a short life cycle advantageous for angiosperms?
It allows quick dispersal, faster reproduction, and competitiveness for space and resources.
314
What advantage do angiosperms have due to advanced vascular tissue?
Their vessel elements efficiently transport water and nutrients, supporting high photosynthetic and growth rates.
315
What are vessel elements and how do they differ from tracheids?
Vessel elements are wider and more efficient at transporting water than tracheids, which are found in gymnosperms.
316
What benefits do seeds provide over spores?
Seeds are protected by a coat, contain nutrients (endosperm), can remain dormant, and disperse effectively in space and time.
317
What is double fertilization and what does it produce?
A process unique to angiosperms where one sperm fertilizes the egg (embryo) and another forms endosperm for nourishment.
318
What is the function of a fruit?
It protects seeds during development and aids in dispersal by animals, wind, or water.
319
What are the main functions of flowers?
They protect reproductive structures, attract pollinators, produce gametes, and facilitate fertilization and seed development.
320
Why are angiosperms more diverse than other plant phyla?
Due to co-evolution with pollinators, genetic mutations, polyploidy, and hybridization leading to speciation.
321
How does co-evolution with pollinators increase diversity?
Small mutations can change flower color or shape, attracting new pollinators and causing reproductive isolation and speciation.
322
What role does genome duplication (polyploidy) play in angiosperm diversity?
It creates genetic redundancy and allows new traits to evolve; 50–70% of angiosperms resulted from polyploidy.
323
What is hybridization and how does it affect angiosperm evolution?
Hybridization between species increases genetic diversity and facilitates new adaptations.
324
How have mangroves adapted to saline environments?
They block salt uptake with roots, reduce water loss via stomata control, and have aerial roots for oxygen intake.
325
What are adaptations of plants to drought?
Features like deep roots, reflective leaf hairs, water storage tissues, and thick waxy coatings reduce water loss.
326
How does the prickly pear cactus adapt to arid environments?
It uses spines (modified leaves), a waxy stem for water storage, and a thick cuticle to minimize evaporation.
327
What are adaptations to desiccation in some angiosperms?
They can lose up to 95% of their water, enter dormancy, and use crystallized sugars to stabilize cells.
328
What are examples of mechanical plant defenses?
Spines and thorns protect against herbivores by deterring physical contact or damage.
329
What are examples of chemical plant defenses?
Plants produce secondary metabolites (e.g., alkaloids, glycosides, tannins) to taste bad or be toxic to herbivores.
330
What are examples of camouflage in plants?
Some plants mimic rocks or surroundings (e.g., pebble plants) to avoid detection by herbivores.
331
What are examples of indirect defenses in plants?
Some, like acacias, form mutualisms with insects (e.g., ants) that defend the plant from herbivores.
332
What is tolerance to herbivory?
Some plants, like grasses, can regrow after being grazed because their growth points are at the base of leaves.
333
How has co-evolution influenced angiosperm diversity?
Interactions with pollinators and herbivores drove adaptation and speciation.
334
What are the main factors that led to angiosperm diversity?
Co-evolution, polyploidy, hybridization, environmental adaptations, and plant–herbivore interactions.
335
When did the first eukaryotic organisms evolve?
Around 2 billion years ago.
336
Which environmental change promoted the evolution of eukaryotes?
The increase in atmospheric oxygen due to photosynthesis by cyanobacteria about 2.5 billion years ago.
337
What happened to most anaerobic prokaryotes when oxygen levels rose?
They went extinct because oxygen was toxic to them.
338
How did some anaerobic prokaryotes survive increased oxygen levels?
By living in oxygen-poor environments or forming endosymbiotic relationships with aerobic prokaryotes.
339
What is symbiogenesis?
The theory that eukaryotic cells evolved from symbiotic relationships between different prokaryotic species.
340
Which two organisms are thought to have formed the first eukaryotic cell?
An asgard archaeon and an alphaproteobacterium.
341
What did the alphaproteobacterium evolve into within the eukaryotic cell?
The mitochondrion.
342
What evidence supports the endosymbiotic origin of mitochondria?
Mitochondria divide independently by binary fission, have circular DNA, ribosomes, and two membranes.
343
Do mitochondria have nuclei?
No, they do not contain a nucleus.
344
What genetic evidence supports symbiogenesis?
Eukaryotic DNA contains genes derived from both archaea and bacteria.
345
What are the advantages of eukaryotic cells over prokaryotic cells?
Protected DNA, ability for sexual reproduction, compartmentalized organelles, and multicellularity.
346
What is one major advantage of having a nucleus?
It protects DNA from damage and allows coordinated cell division (mitosis and meiosis).
347
Why did organelles increase eukaryotic complexity?
They separate cellular functions, increase efficiency, and allow specialization and tissue formation.
348
What are advantages of asexual reproduction?
Fast population growth, no need for a mate, and all individuals can reproduce.
349
What are advantages of sexual reproduction?
Produces genetic variation, enables faster adaptation, and reduces competition within species.
350
How does meiosis contribute to genetic variation?
Through recombination and independent assortment, creating unique offspring.
351
Why might sexual reproduction have evolved despite being costly?
It enhances adaptability and survival under changing environmental conditions.
352
What additional advantage does meiosis provide?
It may repair damaged DNA through homologous recombination.
353
From which process did meiosis likely evolve?
From mitosis or prokaryotic sexual processes like conjugation and transformation.
354
What is a haploid-dominant life cycle?
Organisms are mostly haploid, with the diploid stage existing only briefly during reproduction (e.g., fungi).
355
What is a diploid-dominant life cycle?
Organisms are multicellular in the diploid stage, with haploid gametes formed during reproduction (e.g., animals).
356
What is a haplodiplontic (alternation of generations) life cycle?
Organisms alternate between multicellular haploid (gametophyte) and diploid (sporophyte) stages (e.g., plants).
357
What type of reproduction do most eukaryotes use?
Sexual reproduction — 99% of eukaryotes are capable of it.
358
Why does the Two Domain hypothesis link eukaryotes to archaea?
Because evidence shows eukaryotes evolved from asgard archaea lineages.
359
What environments can prokaryotes live in?
Prokaryotes live everywhere—from frozen ice to hot springs and salt lakes—thanks to their diverse adaptations.
360
What are endospores and their function?
Endospores are dormant, resistant structures that allow prokaryotes to survive heat, drought, and harsh conditions.
361
What is the VBNC state?
The viable-but-non-culturable state allows prokaryotes to survive unfavorable conditions and resume growth later.
362
How do prokaryotes reproduce?
They reproduce asexually by binary fission, producing genetically identical clones.
363
Why do prokaryotic populations evolve quickly despite reproducing asexually?
Due to rapid reproduction, mutations, and horizontal gene transfer.
364
What is horizontal gene transfer?
The movement of genetic material between organisms other than by descent, increasing genetic diversity.
365
How can antibiotic resistance spread among bacteria?
Through horizontal gene transfer—plasmids or DNA fragments can be shared between bacteria.
366
What are the three main metabolic types of prokaryotes?
Chemoautotrophs, photoautotrophs, and chemoheterotrophs.
367
What roles do cyanobacteria play in ecosystems?
They photosynthesize, produce oxygen, fix nitrogen, and form the base of many aquatic food webs.
368
What caused the oxygen revolution?
Cyanobacteria produced oxygen via photosynthesis, increasing atmospheric O₂ about 2.5 billion years ago.
369
Why was the oxygen revolution catastrophic for some organisms?
Oxygen was toxic to anaerobic organisms, causing mass extinctions.
370
How did the oxygen revolution benefit other organisms?
It enabled the evolution of aerobic metabolism and eukaryotes.
371
What are methanogens and where are they found?
Anaerobic archaea that produce methane; found in wetlands, sewage, and animal digestive systems.
372
What is the chemical equation for methanogenesis?
CO₂ + 4H₂ → CH₄ + 2H₂O
373
What are thermophiles?
Organisms that thrive in extremely hot environments, such as hot springs or hydrothermal vents.
374
How do thermophilic archaea survive high temperatures?
They have unique membranes with ether linkages, isoprene sidechains, phospholipid monolayers, and heat-stable enzymes.
375
What are mesophiles?
Prokaryotes that thrive in moderate environments like soil, water, and the human body.
376
What are halobacteria and where do they live?
Salt-loving archaea (halophiles) that thrive in very saline environments like the Dead Sea.
377
What protein helps halobacteria survive high salinity?
Halorhodopsin, a light-activated chloride pump that prevents water loss by maintaining osmotic balance.
378
What is the relationship between Rhizobium and legumes?
A mutualistic relationship—Rhizobium fixes nitrogen for the plant in exchange for glucose.
379
What is a mutualistic relationship?
A symbiotic interaction where both species benefit.
380
What is Bifidobacterium lactis and where is it found?
A gram-positive bacterium found in the digestive system that aids digestion and inhibits harmful bacteria.
381
What are decomposers and their ecological role?
Chemo-organo-heterotrophic bacteria that break down organic matter, releasing CO₂ and ammonium.
382
What is the role of nitrogen-fixing bacteria like cyanobacteria?
They convert atmospheric nitrogen (N₂) into ammonium (NH₄⁺), making nitrogen available to other organisms.
383
What are nitrifying bacteria and their role?
Chemoautotrophs that oxidize inorganic nitrogen compounds to forms plants can absorb.
384
How do prokaryotes contribute to the carbon cycle?
Decomposers release CO₂ during the breakdown of organic matter, recycling carbon.
385
How do prokaryotes contribute to the nitrogen cycle?
By fixing nitrogen, nitrifying ammonia, and decomposing organic material.
386
Why can prokaryotes adapt so quickly?
Because of rapid reproduction, genetic mutations, and horizontal gene transfer.
Fall 2025
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