Biology Midterm 2: Evolution, Plants, Fungi & Animals

What is a major difference between prokaryotic and eukaryotic cells?

Prokaryotes lack a membrane-bound nucleus and organelles, while eukaryotes have a membrane-enclosed nucleus and compartmentalized organelles.

What is peptidoglycan and in which organisms is it found?

Peptidoglycan is a polymer of sugars and amino acids found in the cell walls of bacteria, providing structural integrity.

How do archaea differ from bacteria in terms of cell wall composition?

Archaea lack peptidoglycan and have cell walls made of other compounds, such as S-layer proteins or pseudomurein.

What is transformation in the context of horizontal gene transfer?

Transformation is the uptake of free, naked DNA from the extracellular environment by a bacterial cell.

Describe conjugation in bacteria.

Conjugation is the direct transfer of genetic material between two bacterial cells through a physical mating bridge or pilus.

What is transduction in bacteria?

Transduction is the transfer of bacterial DNA mediated by a virus, specifically a bacteriophage.

What are phototrophs?

Phototrophs are organisms that harness light energy to synthesize ATP through photophosphorylation.

What distinguishes autotrophs from heterotrophs?

Autotrophs fix inorganic carbon to build organic compounds, while heterotrophs absorb preformed organic carbon from the environment.

What significant event did cyanobacteria trigger in Earth's atmosphere?

Cyanobacteria evolved oxygenic photosynthesis, releasing free O2 and precipitating the Great Oxidation Event.

What was the ecological impact of the rise of atmospheric O2?

The rise of atmospheric O2 was toxic to obligate anaerobes, causing mass extinctions, but it also formed the ozone layer and enabled aerobic respiration.

Why is O2 considered a superior electron acceptor?

O2 is highly electronegative, allowing for a significant drop in free energy during electron transport, yielding more ATP than anaerobic electron acceptors.

What role do nitrogen-fixing bacteria play in the nitrogen cycle?

Nitrogen-fixing bacteria convert atmospheric N2 into bioavailable ammonia (NH3/NH4+), making nitrogen accessible to primary producers.

What are the major organelles found in eukaryotic cells?

Major organelles include mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes/vacuoles.

What is the function of the cytoskeleton in eukaryotic cells?

The cytoskeleton provides structural support, enables cellular motility, and facilitates transport within the cell.

What is the nuclear envelope and its significance?

The nuclear envelope is a double-membrane barrier that encloses the genome, allowing for separation of transcription and translation processes.

What is primary endosymbiosis?

Primary endosymbiosis occurs when an ancestral eukaryote engulfs a free-living bacterium, leading to the formation of mitochondria and chloroplasts.

What is secondary endosymbiosis?

Secondary endosymbiosis is when a non-photosynthetic eukaryote engulfs a photosynthetic eukaryotic cell, such as a red or green alga.

What evolutionary advantages does the nuclear envelope provide?

The nuclear envelope separates transcription from translation, allows post-transcriptional processing, and enhances gene expression regulation.

What was the ecological characteristic of Ediacaran fauna?

Ediacaran fauna were soft-bodied, radially symmetric or unsegmented organisms with little evidence of predation or hard shells.

What characterized the Cambrian explosion?

The Cambrian explosion involved rapid diversification of major bilateral body plans and the evolution of hard exoskeletons and predatory lifestyles.

What environmental factor triggered the Cambrian explosion?

A significant rise in atmospheric and oceanic O2 levels enabled high metabolic costs associated with active locomotion and predation.

What is the significance of the nitrogenase enzyme complex in nitrogen-fixing bacteria?

The nitrogenase enzyme complex allows nitrogen-fixing bacteria to convert inert N2 gas into bioavailable ammonia, crucial for the nitrogen cycle.

What is the role of the S-layer in archaea?

The S-layer is a surface-layer protein or glycoprotein sheet that forms part of the cell wall in archaea, providing structural support.

What is the primary energy source for chemoorganotrophs?

Chemoorganotrophs oxidize high-energy organic compounds to generate ATP via cellular respiration or fermentation.

What is the significance of the Great Oxidation Event?

The Great Oxidation Event marked the transition of Earth's atmosphere to one rich in oxygen, enabling the evolution of aerobic life.

What characterizes chloroplasts in certain eukaryotes?

Chloroplasts are surrounded by 3 or 4 membranes, including inner bacterial membranes and engulfed algal membranes.

How many times did multicellularity evolve independently?

Multicellularity evolved independently dozens of times across eukaryotes.

What is one advantage of multicellularity over a single large cell?

Multicellularity overcomes surface-area-to-volume (SA:V) limits, maintaining high SA:V ratios across small individual cells.

What is cellular specialization?

Cellular specialization refers to different cells differentiating for dedicated tasks, increasing physiological efficiency.

What are the photosynthetic pigments shared between plants and green algae?

Chlorophyll a and b, and β-carotene.

What are the benefits of a terrestrial lifestyle for plants?

Abundant sunlight, higher atmospheric CO2 concentration, and nutrient-rich soil.

What adaptation helps prevent water loss in terrestrial plants?

A waxy, hydrophobic cuticle paired with regulated stomata.

What structural support adaptation do plants have against gravity?

Rigid cell walls reinforced with lignin.

What is the role of xylem in plants?

Xylem conducts water and dissolved minerals unidirectionally from roots to shoots.

What is the function of phloem in plants?

Phloem transports sugars, amino acids, and chemical messengers multidirectionally from source tissues to sink tissues.

What is the significance of multicellular gametangia?

They produce gametes, with archegonia producing eggs and antheridia producing sperm.

What is alternation of generations in land plants?

A life cycle alternating between a multicellular haploid (n) gametophyte and a multicellular diploid (2n) sporophyte.

What are embryophytes?

Land plants with multicellular, dependent embryos retained and nourished by maternal female gametophyte tissues.

What is the role of sporopollenin in plant spores?

Sporopollenin encases spores in a durable polymer to withstand desiccation.

What is the difference between homospory and heterospory?

Homospory produces a single type of spore, while heterospory produces two distinct spore types: microspores and megaspores.

What is primary growth in plants?

Primary growth increases plant length/height, initiated by cell divisions in apical meristems.

What is secondary growth in plants?

Secondary growth increases plant thickness/girth, driven by lateral meristems like vascular cambium and cork cambium.

What are the main differences in dominant stages among land plant groups?

Bryophytes have a dominant gametophyte stage, while seedless vascular plants, gymnosperms, and angiosperms have a dominant sporophyte stage.

What is the vascular system's role in plants?

The vascular system facilitates long-distance transport of water, nutrients, and photosynthates.

What is the significance of reduced gametophytes in seed plants?

They are protected within parental sporophyte tissues, obtaining nutrition and protection from environmental stresses.

What adaptations do plants have for reproduction without standing water?

Desiccation-resistant walled spores, multicellular gametangia, and internal fertilization leading to retained embryos.

What is the role of apical meristems in plants?

Apical meristems are regions of continuous cell division at root and shoot tips, driving directional growth.

What are the three types of plant tissue systems?

Dermal tissue, ground tissue, and vascular tissue.

What is the function of guard cells in plants?

Guard cells regulate the opening and closing of stomata for gas exchange.

What is the composition of ground tissue in plants?

Ground tissue is composed of parenchyma, collenchyma, and sclerenchyma cells, performing photosynthesis and storage.

What is the difference in vascular bundle arrangement between eudicot and monocot stems?

In eudicot stems, vascular bundles form a ring; in monocot stems, they are scattered throughout the ground tissue.

What is an ovule?

A megasporangium enclosed by protective sporophyte integuments that retains the megaspore and female gametophyte.

What is pollen?

A tough, sporopollenin-coated microgametophyte that allows fertilization without free-standing water.

What are the major differences between mosses and ferns?

Mosses are nonvascular and gametophyte-dominant, while ferns have a vascular system and are sporophyte-dominant.

What type of tissue is the nutritive tissue for embryos in gymnosperms?

Haploid (n) female gametophyte tissue.

What is the process of double fertilization?

One sperm fertilizes the egg to form a diploid zygote, and the other sperm fuses with two polar nuclei to form triploid endosperm.

What distinguishes pine trees from Ohio buckeye?

Pine trees produce cones (gymnosperms), while Ohio buckeye produces flowers (angiosperms).

Where is pollen produced in flowering plants?

Inside the anthers of the male stamens.

Where does the egg reside in angiosperms?

Inside the female gametophyte (embryo sac) within an ovule in the ovary of the carpel.

What are lichens?

Mutualistic associations between fungi and photosynthetic partners like green algae or cyanobacteria.

What are mycorrhizae?

Symbiotic associations between fungi and plant roots that enhance nutrient and water absorption.

What is the role of ectomycorrhizal fungi?

They form an outer sheath around root tips and penetrate between cortical cells.

What is the function of endomycorrhizal fungi?

They penetrate root cortical cell walls and form arbuscules in direct contact with host plasma membranes.

What is the body plan of fungi?

Fungi consist of hyphae that form a mycelium, providing a large surface area for absorption.

What is the nutritional mode of fungi?

Fungi are absorptive heterotrophs that secrete enzymes to digest food externally before absorption.

What is the significance of chitin in fungi?

Chitin is a structural component found in fungal cell walls, similar to arthropod exoskeletons.

What is the dominant stage in the life cycle of mosses?

Gametophyte-dominant (n).

What is the dominant stage in the life cycle of ferns?

Sporophyte-dominant (2n).

What type of flowers do beetles prefer?

Dull/white or greenish bowl-shaped flowers with strong fruity or foul scents.

What type of flowers attract moths?

White or pale tubular flowers that open at night and emit strong sweet fragrances.

What type of flowers are favored by hummingbirds?

Vivid red or orange tubular flowers that are odorless and produce abundant nectar.

What type of flowers do bats prefer?

Large, sturdy, dish-shaped dull or white flowers that open at night and produce copious nectar.

What is the role of endophytes in plants?

Endophytes live inside plant tissues and may produce toxic compounds to deter herbivores.

What is the significance of the vascular system in ferns?

Ferns possess a vascular system (xylem and phloem) for efficient transport of water and nutrients.

What are the reproductive structures of fungi called?

Dense, compact hyphal structures that produce and disperse spores, such as mushrooms.

What is the primary function of hyphae in fungi?

Hyphae increase surface area for absorption of nutrients from the environment.

What is the difference between gymnosperms and angiosperms in terms of seed production?

Gymnosperms produce naked seeds, while angiosperms produce seeds enclosed in fruits.

What are the key characteristics of animals?

Multicellular eukaryotes lacking cell walls, ingestive heterotrophs, possess nerve and muscle tissue (except sponges), and undergo distinctive embryonic development with blastula formation.

What is asymmetry in animals?

A lack of any plane of symmetry, as seen in Porifera (sponges).

Define radial symmetry.

Body arranged around a central axis with multiple planes producing mirror-image halves, as in adult Cnidaria and Ctenophora.

What is bilateral symmetry?

A body plan with a single sagittal plane creating distinct left and right halves, often accompanied by cephalization.

What are the three embryonic germ layers?

Ectoderm (outer covering and nervous system), endoderm (inner lining of digestive tract), and mesoderm (muscle and internal organs).

What distinguishes diploblastic from triploblastic animals?

Diploblasts have two germ layers (ectoderm and endoderm), while triploblasts have three (ectoderm, mesoderm, and endoderm).

What is an incomplete gut?

A digestive system with a single opening serving as both mouth and anus, found in organisms like Cnidaria.

What is a complete gut?

A one-way digestive tract extending from mouth to anus, allowing for specialized digestive compartments.

What is the function of a coelom?

It cushions internal organs, allows for independent growth and movement of organs, and serves as a hydrostatic skeleton.

List the five major lineages of animals.

1. Porifera (sponges), 2. Ctenophora (comb jellies), 3. Cnidaria (jellyfish, corals), 4. Protostomes, 5. Deuterostomes.

What are the growth modes in protostomes?

Lophotrochozoans exhibit continuous growth, while Ecdysozoans grow by molting their exoskeleton.

What are the general features of arthropods?

Segmented bodies, jointed chitinous exoskeleton, and paired jointed appendages.

What are the main lineages of arthropods?

1. Chelicerata (spiders, scorpions), 2. Myriapoda (centipedes, millipedes), 3. Crustacea (shrimp, crabs), 4. Hexapoda (insects).

Describe hemimetabolous development.

Incomplete metamorphosis where the organism develops through a series of nymphal instars resembling mini-adults.

Describe holometabolous development.

Complete metamorphosis involving distinct life stages: egg, larva, pupa, and adult.

What is the phylogenetic order of vertebrate traits?

1. Notochord, 2. Vertebrae, 3. Hinged jaws, 4. Lungs, 5. Lobed fins, 6. Limbs with digits, 7. Amniotic egg, 8. Lactation/milk.

What adaptations did vertebrates develop for life on land?

Internal lungs for respiration, robust tetrapod limbs for support, and the amniotic egg to prevent desiccation.

What are the three groups of mammals based on reproduction?

1. Monotremes (lay eggs), 2. Marsupials (give birth to underdeveloped young), 3. Placentals (extended gestation with placenta).

What are the advantages of viviparity in mammals?

Offspring develop in a controlled environment, protected from predators and harsh conditions, allowing mothers to remain mobile.

What are the trade-offs of placental gestation?

Energetically expensive for the mother, limits litter size, and can increase maternal mortality risk.

What is the significance of feathers in birds?

Initially evolved for insulation and display, later adapted for flight.

How are birds classified phylogenetically?

Birds are modern avian dinosaurs and are classified within the Reptilia clade.