Midterm 2

Question 1

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

Answer 1

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.

Question 2

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

Answer 2

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.

Question 3

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

Answer 3

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

Question 4

What are the mechanisms that create genetic variation in prokaryotes?

Answer 4

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.

3. Genetic recombination - when genetic material is exchanged between individual cells (prokaryotes do this).

Question 5

What is horizontal gene transfer?

Answer 5

When genetic recombination occurs between individuals from different species.

Question 6

What are the three forms of genetic recombination?

Answer 6

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.

Question 7

What is the endosymbiont theory?

Answer 7

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

Question 8

What is serial endosymbiosis?

Answer 8

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

Question 9

What is secondary endosymbiosis?

Answer 9

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

Question 10

What is the excavata clade in the diversity of protists?

Answer 10

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

Question 11

What is the SAR clade in the diversity of protists?

Answer 11

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

• contribute significantly to eukaryotic diversity

Question 12

What is the Archaeplastida clade in the diversity of protists?

Answer 12

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

Question 13

What is the Unikonta clade in the diversity of protists?

Answer 13

Includes protists closely affiliated with fungi and animals.

Question 14

What is a protist?

Answer 14

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

Question 15

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

Answer 15

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.

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Bryophytes are categorized into liverworts, mosses, and hornworts

Question 18

What are some characteristics of bryophytes?

Answer 18

• 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.

Question 19

What are the shared, derived traits of vascular plants?

Answer 19

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

Question 20

What are the two classifications of vascular plant leaves?

Answer 20

Microphylls - small leaves with single veins

Megaphylls - large leaves with highly branched vascular systems

Question 21

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

Answer 21

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

Question 22

What are some shared, derived traits of gymnosperms?

Answer 22

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

Question 23

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

Answer 23

Gymnosperms (conifers) - means naked seeds

Angiosperms (flowering plants)

Question 24

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

Answer 24

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

Question 25

What is the structure of a stamen?

Answer 25

Stamen (or microsporophyll) consists of a stalk (filament) topped with an anther - the anther contains pollen sacs (microsporangia) that produce pollen

Question 26

What is the structure of a carpel?

Answer 26

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.

Question 27

What are the shared, derived traits of fungi?

Answer 27

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

Question 28

What are chytrids?

Answer 28

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

Question 29

What are zygomycetes?

Answer 29

a paraphyletic group that produces hyphae without septa (coenocytic) - reproduce asexually through the formation of zygosporangia, which form after fusion of specialized hyphae

Question 30

What are glomermycetes?

Answer 30

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

Question 31

What is Dikarya fungi?

Answer 31

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

Question 32

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

Answer 32

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

Question 33

What is Ascomycetes?

Answer 33

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

Question 34

What is Basidiomycetes?

Answer 34

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

Question 35

What are a fungi's hyphae?

Answer 35

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

Question 36

What are the three fungal pathogens?

Answer 36

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

Question 37

What is ectomycorrhizal fungi?

Answer 37

Envelop roots of plants without penetrating the root cells

Question 38

What is endomycorrhizal fungi?

Answer 38

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

Question 39

What are the adaptations of land plants? (T13)

Answer 39

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)

Question 40

What are the 5 prokaryote adaptations?

Answer 40

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

Question 41

Prokaryote adaptations 1. Cell Surface Structures

Answer 41

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

Question 42

Prokaryote Adaptations 2. Endospores

Answer 42

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).

Question 43

Prokaryote Adaptations 3. Motility

Answer 43

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

Question 44

Prokaryote adaptations 4. simple internal organization and DNA

Answer 44

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

Question 45

Prokaryote Adaptations 5. Reproduction

Answer 45

Prokaryotes reproduce quickly by binary fission (when DNA is copied and the cell splits) - binary fission is asexual reproduction since prokaryotes are unicellular

Question 46

What is prokaryote metabolic diversity?

Answer 46

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

Question 47

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

Answer 47

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

Question 48

What are obligate aerobes & obligate anaerobes?

Answer 48

obligate aerobes - depend on O2 for cellular respiration obligate anaerobes - inhibited by O2 (diverse metabolism for oxygen & nitrogen)

Question 49

What is Biological Nitrogen Fixation?

Answer 49

When atmospheric nitrogen (N2) is converted to ammonia (NH3) - certain prokaryotes and bacteria play a crucial role in this