EXAM 2 Objectives

explain the importance of nodes on a phylogenetic tree in determining evolutionary relationships

they represent the common ancestors of those descendants

includes all the groups we are interested in figuring out relationships

ingroup

a group of organisms that don’t belong to those being studied

outgroup

contains an ancestor and all of its descendants

monophyletic group

contains a common ancestor and only some of the descendants of that ancestor

paraphyletic group

do not share a common ancestor

polyphyletic group

save function & evolutionary origin

homologous characters

similar function but different evolutionary origin

analogous characters

belongs to everyone in the group

ancestral characters

new trait that evolved within a smaller group of organisms

derived characters

what is the role of synapomorphies (derived characters) in constructing a phylogenetic tree

they provide evidence of evolutionary relationships & help determine which groups share a common ancestor

explain the utility of molecular data in constructing a phylogenetic tree

they compare the sequences of their evolutionary related genes/proteins

explain the principle of parsimony regarding phylogenetic trees

2 hypotheses about vertebrate relationships

what is the importance of sex in maintaining genetic diversity?

allows for the mixing & combination of genes from 2 individuals, creating new genetic combinations in offspring (it does not always increase variation)

zygotic meiosis

haplontic life cycle

gametic meiosis

diplontic life cycle

sporic meiosis

haplodiplontic life cycle (alternation of generations)

explain why protists are a paraphyletic grouping of organisms

it doesn’t contain all descendants of its most recent common ancestor

what are the different modes of locomotion & nutritional strategies of protists

flagella, cilia, & pseudopodia

explain why protists, algae, and protozoa form paraphyletic groups within the eukaryotes

the representative taxa don’t contain all the descendants of their stem species

explain the importance of surface area-to-volume ratio in cell size

to ensure that the exchange of resources & waste occurs quickly enough for the cell to survive

single celled micro-organisms with a defined nucleus, mitochondria, and other organelles

unicellular

Composed of multiple cells that are similar to one another, often found in algae

• Colonial organisms

simple multicellular

requires cell adhesion, cell communication, & specialized tissues

complex multicellular

evaluate the role of bulk flow in multicellular organisms

it allows for rapid exchange of gases between cells

describe why complex multicellularity requires cell adhesion, communication, & a genetic program for development

it enable cells to stick together, coordinate their actions, and differentiate into specialized tissues, allowing for the formation of intricate structures and functions within a multicellular organism, which would be impossible without such coordinated control and interaction between individual cells

describe the basic body plan of a fungus

the cell walls are made of chitin, body of fungi form a network of hyphae which is called a mycelium which infiltrate the food for the fungus

explain why the body design of fungi suits their form of heterotrophy

the thin, filamentous hyphal structure allows for maximal surface area and thus, maximal contact with the food substrate

discuss how fungal feeding is related to fungal growth

• Fungi can grow quickly when food is plentiful (grows at the edges)

• Branches create high surface area from absorption

• Osmosis is important so the hyphal tips can swell and produces force for tip expansion

explain the difference btwn the cell walls of plants & fungi

plant cells maintain their shape with a cell wall made of cellulose & fungi have a cell wall made of chitin

distinguish btwn different kinds of symbiotic relationships involving fungi

mycorrhiza (fungi & plant roots) and lichens (fungi & cyanobacteria/green algae)

group of fungi that act as decomposers, feeding on dead & decaying wood, leaves, litter, & other organic matter. break down cellulose & lignin from wood

saprobes

they benefit to the detriment (and sometimes death) of their host

parasites

fungi attack nematodes & other microorganisms using a remarkable array of trapping devices to attract, capture, kill, & digest nematodes for food

predators

mutualists

explain why saprobic fungi are critical to earth’s carbon cycle

Were it not for the fungal decomposers, Earth's carbon cycle would fail. Great quantities of carbon atoms would remain trapped forever on forest floors and elsewhere. Instead, those carbon atoms are returned to the atmosphere in the form of CO2by fungal respiration, where they are again available for photosynthesis by plants

scavenge for nutrients released by saprotrophic microbes

arbuscular mycorrhizae

mineralize nutrients from organic matter and can thus access some forms of organic N directly

ectomycorrhizae

benefits of mycorrhizal associations

Mycorrhizal associations benefit both the fungus and the plant by the fungus getting organic compounds such as sugars and amino acids from plants. In return, the fungus allows the plant to better absorb water and minerals

explain the unique aspects of the fungal life cycle

Perfect fungi are sexually and asexually replicated, whereas imperfect fungi are only asexually reproduced (by mitosis)

single individual produces an offspring the same genetic makeup as the parent (binary fission & mitosis)

asexual reproduction

two parents combine their genetic makeup to create an offspring with a unique genetic makeup (meiosis & fertilization)

sexual reproduction

why are fungi more closely related to animals than plants?

they are heterotrophic

explain what’s meant by alternation of generations

plants alternate between two different life stages, or generations, in their life cycle

summarize the features that distinguish bryophytes from other plants

they have no vascular system, they absorb water & nutrients through body surface from soil

discuss the features that distinguish seedless vascular plants from algae & bryophytes

seedless vascular plants have several adaptations that algae and bryophytes lack, including vascular tissues and a dominant sporophyte generation. As in bryophytes, reproduction in seedless vascular plants depends on water as a transport medium for motile sperm cells.

leaves of small size with one vein & associated with steles that lack leaf gaps (lycophytes)

microphylls

leaves of large size with complex veins & associated with leaf gaps in the stele (ferns)

megaphylls

describe the difference btwn homospory & heterospory

homospory refers to the production of identical spores in size and shape. Heterospory refers to the production of two different types of spores

(earliest vascular plants: homospory; evolved multiple times: heterospory)

explain how the evolution of pollen enabled seed plants to thrive in terrestrial environments

allowed plants to reproduce without water

explain how seeds are an adaptation to a terrestrial environment

they allow plants to survive in dry conditions and reproduce without a constant water supply

explain the role of flowers in the evolutionary success of angiosperms

attract pollinators and protect their seeds

explain the role of fruits in the evolutionary success of angiosperms

providing protection and nutrition to the developing seeds, while ensuring the efficient dispersal upon maturity

explain how the evolution of alternation of generations makes plants well adapted for reproduction on land

allowed plants to thrive on land because the haploid spores produced by the sporophyte can disperse over large distances without the need for water

how is fern reproduction similar to moss reproduction?

Both moss and ferns exhibit alternation of a haploid generation and a diploid generation.

how is fern reproduction different from moss reproduction

in ferns, the sporophyte is only initially dependent on the gametophyte and eventually becomes free-living

in mosses, the sporophyte is completely dependent on the gametophyte.

describe the life cycle of a typical gymnosperm & give the major reproductive adaptations that evolved in gymnosperms

involves alternation of generations, with a dominant sporophyte in which the female gametophyte resides, and reduced gametophytes

all gymnosperms are heterosporous. The male and female reproductive organs can form in cones or strobili

explain the evolutionary significance of the pollen tube

allowing seed plants to reproduce on land without the need for water

parts of each whorl of a flower

calyx, corolla, androecium, gynoecium

consists of flattened sepals

• usually outermost whorl

• protect flower in bud

• enhances reproductive sucess

calyx

consists of petals

• may be fused

• function to attract pollinators

• enhances reproductive success

corolla

collective terms for stamens

• stamen consists of a filament & anther

• filament “stalk” is often threadlike

• 4 microsporangia at apex in swollen portion (anther)

androecium

collective term for carpel(s)

• carpel consists of ovary, style, & stigma

• ovules produced in ovary

• ovary is the swollen lower portion (protecting ovules which develop into seeds)

gynoecium

describe how the flower forms pollen grains & ovules

pollen grains are produced within the anther, which is part of the male reproductive organ called the stamen, while ovules are formed inside the ovary, which is part of the female reproductive organ known as the pistil

describe the structure of the angiosperm female gametophyte

characterize the phenomenon of double fertilization in angiosperms in terms of the resulting zygote and endosperm

it involves two sperm cells; one fertilizes the egg cell to form the zygote, while the other fuses with the two polar nuclei that form the endosperm

explain how pollen & seeds are an adaptation to a terrestrial environment

they allow plants to reproduce effectively on land without the need for water to transport sperm

explain the relationships among ovules, seeds, & fruits

ovules are structures with the potential to develop into seeds & ovaries are structures with the potential to develop into fruits. Seeds are enclosed within fruits, which are mature, ripened ovaries.

explain the need for dispersal

it allows individuals to move away from their natal area, reducing competition for resources with their parents and siblings, avoiding inbreeding, and accessing new habitats with potentially better conditions for growth and reproduction, thus increasing the chances of successful establishment and population spread

what is the role of spores in plant dispersal?

to be dispersed via wind/water, allowing plants to spread their offspring far away from the parent plant to new locations

what is the role of seeds in plant dispersal?

transport to new sites for germination and the establishment of new individuals

describe the modes of asexual reproduction that occur in flowering plants

apomixis & vegetative reproduction

contrast the ways in which bryophytes and vascular plants cope with fluctuation in water availability

bryophytes rely on their ability to rapidly absorb water from the surrounding environment when it is available, essentially becoming saturated.

vascular plants utilize a complex root system and specialized tissues to transport water efficiently, allowing them to tolerate drier conditions by regulating water loss through stomata and adapting their root structure to access deeper water sources when necessary

• components: epidermis & periderm

• functions: protection & prevention of water loss

dermal tissue system

• components: parenchyma tissue, collenchyma tissue, & schlerenchyma tissue

• functions: photosynthesis, food storage, regeneration, support, & protection

ground tissue system

• components: xylem & phloem tissue

• functions: transport of water & minerals & transport of food

vascular tissue system

explain why obtaining CO2 from the air results in high rates of water loss

plants can partially close these stomata to maintain optimal carbon uptake

how does the cuticle & stomata allow leaves to control water loss?

thick waxy cuticles (the coating on leaves) create a barrier to evaporation

contrast how the waxy cuticle helps the leaf slow rates of water loss, but in doing so, also slows the diffusion of CO2 into leaves

the cuticle reduces the rate of water loss from the leaf surface. They can also reduce the rate of transpiration by blocking air flow across the leaf surface; When stomata close, cuticle waxes on the epidermal tissues increasingly affect this diffusion.

• separation of initial CO2 fixation & Calvin cycle: no separation

• stomata open: day

• best adapted to: cool, wet environments

C3 photosynthesis

• separation of initial CO2 fixation & Calvin cycle: no separation: btwn mesophyll & bundle-sheath cells (in space)

• stomata open: day

• best adapted to: hot, sunny environments

C4 photosynthesis

• separation of initial CO2 fixation & Calvin cycle: no separation: btwn night & day (in time)

• stomata open: night

• best adapted to: very hot, dry environments

CAM photosynthesis

structure of xylem

the xylem tracheary elements consist of cells known as tracheids and vessel members, both of which are typically narrow, hollow, and elongated

differentiate between tracheids and vessel elements

tracheids are made up of single cells & vessels are made up of a group of cells

explain how water’s moved from roots to leaves of plants

through tissue called the xylem, in a process called transpiration

relate the movement of water in xylem to the properties of water

adhesion and cohesion allow the formation of a continuous column of water in the xylem

explain how transpiration provides the force that pulls water up the stem from the roots through xylem conduits with thick, lignified cell walls

causing water to evaporate from the leaves, generating a negative pressure (tension) that draws water upwards from the roots through the continuous column of water held together by cohesion (water molecules sticking to each other) and adhesion (water molecules sticking to the xylem cell walls)

in plants, they’re responsible for synthesizing the sugars required for plant growth

source tissues

in plants, they use the sugars for immediate use and store the rest for future metabolic needs

sink tissues

relate the structure of phloem cells to their function in moving carbohydrates from sources to sinks

each component functions together to enhance the transfer of carbohydrates and amino acids from a source to sink tissues, where they are utilized or stored

explain the pressure-flow mechanism of sugar transport in phloem

movement of water into the phloem creates turgor pressure in the phloem. the high turgor pressure forces movement of phloem sap from source to sink through a process called “bulk flow.” The sugars moved via bulk flow are then rapidly removed from the phloem at the sink

identify and describe the pathways water and minerals can take from the root hair to the vascular tissue

the apoplastic pathway (through the cell walls) and the symplastic pathway (through the cytoplasm of cells)

explain the role of the endoderm & Casparian strip in allowing roots to be selective in which nutrients they take in from the soil

the casparian strip prevents water and nutrients from entering the stele through an apoplast pathway

describe the modular nature of plant structure

construction of repeating units known as modules

explain the role of the apical meristem in plant growth patterns

trigger the growth of new cells in young seedlings at the tips of roots and shoots and forming buds

explain why an expanding internode cell grows more in length than in width

the wall is more extensible in one direction than another (it is easier to extend in the direction that is parallel to the long axis of the stem than it is in the direction perpendicular to the long axis of the stem)

explain how root development is similar to & different from stem development

both roots and stems grow from apical meristems, have regions of cell division, elongation, and differentiation, and respond to light and gravity. However, root apical meristems are covered by a root cap, the root has a single vascular bundle in the center, and branching occurs by the formation of new meristems from the pericycle; all these features are different from what is seen in stems.

lateral meristem that produces new xylem & phloem

vascular cambium

lateral meristem that maintains a protective layer of bark, replacing the epidermis as the plant grows thicker

cork cambium

• synthesis & transport:

  • produced primarily in SAM & tips young leaves/transported by polar transport & through phloem

• effects:

  • cell elongation & expansion (cell enlargement)

  • suppression of lateral bud growth (apical dominance)

  • flowering, fruit ripening, & inhibition of abscission (leaf falling)

  • tropisms ex: phototropism & gravitopism (geotropism)

auxin