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BIOL 108 > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

What are fossils? What type of rock are they associated with?

A

Fossils are preserved evidence of organisms that lived in the past.

  • Associated with sedimentary rock (strata)
  • Fossils are used to calibrate phylogenies, record extinct species, and link evolutionary events with geological changes.
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2
Q

What are the two most notable mass extinctions? When did they occur?

A

Permian mass extinction happened 252 mya. It linked the Paleozoic & Mesozoic Eras.

  • About 60% of all biological families went extinct, and was the earth’s most severe extinction event.
  • The cause? A catastrophic environmental change due to volcanic activity.

Cretaceous mass extinction happened 66 mya. It separates the Mesozoic and Cenozoic eras.

  • 20% of all families went extinct, and it was caused by a meteorite impact proven by the presence of iridium in sedimentary rock.
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3
Q

What is the hypothesized sequence of stages of the chemical and physical process to produce simple cells?

A
  1. Abiotic synthesis of small organic molecules
  2. Joining of small organic molecules into organic polymers (organic macromolecules)
  3. Packaging of molecules into protocells
  4. Origin of self-replicating molecules
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4
Q

What are the mechanisms that create genetic variation in prokaryotes?

A
  1. Rapid reproduction through binary fission (rapid generation of genetically diverse populations)
  2. Mutations
    - Binary fission is asexual reproduction, which means mutation rates are low, but mutations can quickly accumulate in a population.
  • Mutations and rapid reproduction means that prokaryotes can evolve quickly too.
  1. Genetic recombination - when genetic material is exchanged between individual cells (prokaryotes do this).
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5
Q

What is horizontal gene transfer?

A

When genetic recombination occurs between individuals from different species.

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6
Q

What are the three forms of genetic recombination?

A
  1. Transformation - absorption and integration of external DNA from the surrounding environment
  2. Transduction - the transfer of DNA segments between bacteria by bacteriophages (viruses that infect bacteria)
  3. Conjunction - when genetic material is exchanged between prokaryotic cells through direct physical contact.
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7
Q

What is the endosymbiont theory?

A

Proposes that mitochondria and plastids (chloroplasts and related organelles) were once small prokaryotes residing within larger host cells.

  • prokatyotic ancestors of mitochondria and plastids likely entered a host cell as undigested prey or as internal parasites
  • As their relationship evolved and they became more dependent on one another, this led to their integration.

Topic 11, slide 6

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8
Q

What is serial endosymbiosis?

A

Hypothesizes mitochondria evolved before plastids in a series of primary endosymbiotic events.

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9
Q

What is secondary endosymbiosis?

A

Eukaryotic cells themselves become endosymbionts, being taken up by other eukaryotic cells.

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10
Q

What is the excavata clade in the diversity of protists?

A

Encompasses unicellular protists with modified mitochondria, and those possessing distinctive flagella

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11
Q

What is the SAR clade in the diversity of protists?

A

Classified based on DNA similarities, and likely evolved through secondary endosymbiosis. They are particularly abundant in ocean ecosystems

  • contribute significantly to eukaryotic diversity
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12
Q

What is the Archaeplastida clade in the diversity of protists?

A

comprises red algae and green algae, serving as the closest relatives to land plants.

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13
Q

What is the Unikonta clade in the diversity of protists?

A

Includes protists closely affiliated with fungi and animals.

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14
Q

What is a protist?

A

any member of a group of diverse eukaryotic, predominantly unicellular, microscopic organisms.

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15
Q

What are the characteristics of land plants? (T13, slide 2)

A

Many characteristics are also present in various protist clades, primarily in algae.

  • Plants are multicellular, photosynthetic (photoautotrophic) eukaryotes
  • Plants possess cell walls made of cellulose
  • Plants have chloroplasts with chlorophyll a and b.
  • Plants store photosynthetic sugars (such as starch) in plastids.
  • life cycles featuring alternation of generations.
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16
Q

What is alternation of generations? (T13, slide 12)

A

The life cycle of land plants alternate between two multicellular generations

  1. The gametophyte produces haploid gametes by mitosis
  2. Two gametes unite (by fertilization) and form a diploid zygote
  3. The zygote develops into a multicellular diploid sporophyte
  4. The sporophyte produces unicellular haploid spores by meiosis
  5. The spores develop into multicellular haploid gametophytes
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17
Q

What are nonvascular plants called? What are the three phyla of nonvascular plants?

A

Bryophytes are categorized into liverworts, mosses, and hornworts

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18
Q

What are some characteristics of bryophytes?

A
  • Bryophytes lack true vascular tissue and lignin. The absence of these makes bryophytes small, and restricts their growth because they have little structural support.
  • bryophytes do not form roots, branches, or leaves
  • mosses and hornworts use stomata for gas exchange, but liverworts do not have stomata.
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19
Q

What are the shared, derived traits of vascular plants?

A
  1. Vascular tissues, which allow sporophytes to grow tall
    - Xylem, which conducts water via dead, hollow cells
    - Phloem, which distributes nutrients and organic products via living cells
  2. Life cycles with dominant sporophytes (not continuously reliant on gametophytes)
  3. Complex multicellular roots and leaves
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20
Q

What are the two classifications of vascular plant leaves?

A

Microphylls - small leaves with single veins

Megaphylls - large leaves with highly branched vascular systems

21
Q

What are sporophylls in vascular plants? What are the two types?

A

Modified leaves bearing sporangia (spore producing organs)

Sori - clusters of sporangia found on the undersides of sporophylls

Strobili - cone-like structures formed from groups of sporophylls

22
Q

What are some shared, derived traits of gymnosperms?

A
  1. gametophytes develop within spore walls retained within parent sporophyte tissues.
    - a trend in plant evolution is the reduction in gametophyte size and independence with an increase in the role of the sporophyte
  2. Heterospory- produce both megaspores (give rise to female gametophytes) and microspores (give rise to male gametophytes)
  3. Ovules - develop into seeds after fertilization
  4. Pollen - microspores develop into male gametophytes within pollen grains
  5. Seeds - a seed develops from a fertilized ovule
23
Q

What are the two living clades of gymnosperms? What are their differences?

A

Gymnosperms (conifers) - means naked seeds

Angiosperms (flowering plants)

24
Q

What is the flower structure and function in angiosperms? (T17, slide 4)

A

Flowers are structures specialized for sexual reproduction.

  • sepals and petals are sterile structures - sepals protect and develop the flower to attract polinators
  • stamens and carpels are reproductive organs responsible for producing spores
25
Q

What is the structure of a stamen?

A

Stamen (or microsporophyll) consists of a stalk (filament) topped with an anther

  • the anther contains pollen sacs (microsporangia) that produce pollen
26
Q

What is the structure of a carpel?

A

A carpel (megasporophyll) consists of an ovary at the base, and style leading up to the stigma where pollen is received.

  • the ovary contains one or more ovules, each of which has the potential to develop into a seed upon fertilization.
27
Q

What are the shared, derived traits of fungi?

A
  1. Absorptive nutrition
    - fungi are absorptive chemoheterotrophs - obtain nutrients by dissolving organic compounds from their environment (absorptive heterotrophs)
  2. Hyphae and mycelia - hyphae are thread-like filaments that collectively form mycelia.
  3. Chitinous cell wall - the flexible chitin cell wall provides structural support and protection
28
Q

What are chytrids?

A

The paraphyletic group with the earliest diverging group of fungi

  • predominantly inhabit aquatic or moist environments
  • zoospores - motile, flagellated, asexual spores unique to chytrids
  • play a diverse role as decomposers, parasites, or mutualists
29
Q

What are zygomycetes?

A

a paraphyletic group that produces hyphae without septa (coenocytic)

  • reproduce asexually through the formation of zygosporangia, which form after fusion of specialized hyphae
30
Q

What are glomermycetes?

A

All form sybiotic relationships with plant roots

  • play a significant ecological role by establishing arbuscular mycorrhizal association (endomycorrhizae) with over 80% of plant species
  • glomeromycetes reproduce primarily by the production of asexual soil spores
31
Q

What is Dikarya fungi?

A

Most fungi belong to this subkingdom - characterized by the formation of septate hyphae and the development of dikaryotic hyphae after plasmogamy

32
Q

What are the two monophyletic groups that dikarya are classified into?

A

Ascomycetes - typically exhibit a brief dikaryotic stage, with plasmogamy and karyogamy occurring in relatively rapid succession.

Basidiomycetes - often maintain a prolonged dikaryotic phase, where dikaryotic hyphae frequently dominate the mycelium structure

33
Q

What is Ascomycetes?

A

The most diverse fungi that thrive in various environments

  • produce sexual spores called asci, which are contained in specialized fruiting bodies known as ascocarps
  • reproduce sexually by the production of vast quantities of asexual spores called conidia
34
Q

What is Basidiomycetes?

A

Include a range of familiar fungi like toadstools, puffballs, shelf fungi, etc.

  • The typical life cycle involves a prolonged phase of dikaryotic mycelium - where two different nuclei co-exist within the same hyphal compartment.
  • club shaped structures called basdia
  • undergo sexual reproduction by generating elaborate, multicellular fruiting bodies known as basdiocarps
35
Q

What are a fungi’s hyphae?

A

Hyphae are thin, tubular cells filled with cytoplasm and organelles

  • make up the mycelium of a fungus
  • the multicellular hyphal morphology enhances fungi’s ability to absorb nutrients
36
Q

What are the three fungal pathogens?

A
  1. Moulds - fast-growing fungi that primarily reproduce asexually.
    - Fuzzy growths of hyphae
  2. Yeasts are unicellular fungi commonly found in liquid or moist environments
    - reproduce asexually by budding off daughter cells after undergoing mitosis
  3. Mycorrhizae - mutually beneficial symbiotic relationships between fungi and the roots of vascular plants
  • The two types of mycorrhizae are ectomycorrhiza and endomycorrhiza
37
Q

What is ectomycorrhizal fungi?

A

Envelop roots of plants without penetrating the root cells

38
Q

What is endomycorrhizal fungi?

A

hyphae of these fungi penetrate the cell walls of root cells, forming intricate invaginations of the root cell membrane

39
Q

What are the adaptations of land plants? (T13)

A
  1. Sporopollenin - incredibly durable polymer in the cell wall secreted by charophyte zygotes
  2. Adaptations for water conservation - waxy cuticle acts as a protective layer covering epidermis - stomata facilitate gas exchange and serve as sites for water evaporation
  3. Lignified vascular tissue for internal transport - xylem transports water and minerals from roots to leaves, phloem are living cells that distribute soluble organic compounds produced during photosynthesis
  4. Functional compartmentalization in terrestrial plants (different functions of leaves and roots)
40
Q

What are the 5 prokaryote adaptations?

A
  1. Cell surface structures
  2. Endospores
  3. Motility
  4. Simple internal organization and DNA
  5. Reproduction
41
Q

Prokaryote adaptations
1. Cell Surface Structures

A

capsule - sticky protein layer that many prokaryotes are surrounded by that allow cells to adhere to one another and surfaces

biofilms - communities of cells in a slimy extracellular matrix (dental plaque)

fimbriae - hair-like appendages that facilitate cell adhesion to substrates, or other cells in a colony

pilli - longer structures unlike fimbriae that play a role in the exchange of DNA

42
Q

Prokaryote Adaptations
2. Endospores

A

Dormant cells that develop within certain prokaryotes when environmental conditions become unfavorable

Metabolically inactive endospores - can endure harsh conditions for as long as decades or centuries. (some prokaryotes produce these).

43
Q

Prokaryote Adaptations
3. Motility

A

Approximately half of all prokaryotes are motile.

flagella - whip-like appendages that allow motile prokaryotes to move

taxes - the ability to move in response to a specific stimulus

44
Q

Prokaryote adaptations
4. simple internal organization and DNA

A

Prokaryotes have no complex compartmentalization.

  • lack membrane enclosed organelles
  • prokaryotes have small genomes that consist of a single circular chromosome
  • plasmids - circular DNA molecules that provide prokaryotes with additional genetic versatility
45
Q

Prokaryote Adaptations
5. Reproduction

A

Prokaryotes reproduce quickly by binary fission (when DNA is copied and the cell splits)

  • binary fission is asexual reproduction since prokaryotes are unicellular
46
Q

What is prokaryote metabolic diversity?

A

Prokaryotes have remarkable metabolic diversity

Metabolism - the chemical pathways used by living organisms to build up or break down molecules to release energy

Build up = anabolism
Break down = catabolism

47
Q

What are phototrophs & chemotrophs? What are Autotrophs and Heterotrophs?

A

Phototrophs - obtain energy from light
Chemotrophs - obtain energy from chemicals

Autotrophs - use simple inorganic molecules as carbon sources
Heterotrophs - require organic substrates to obtain carbon

48
Q

What are obligate aerobes & obligate anaerobes?

A

obligate aerobes - depend on O2 for cellular respiration

obligate anaerobes - inhibited by O2

(diverse metabolism for oxygen & nitrogen)

49
Q

What is Biological Nitrogen Fixation?

A

When atmospheric nitrogen (N2) is converted to ammonia (NH3)

  • certain prokaryotes and bacteria play a crucial role in this

BIOL 108 (13 decks)

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