BSC2011 Exam 1

3 Domains of Life

Bacteria, Archaea, Eukarya

Photosynthesis Inputs

Carbon Dioxide and Water

Photosynthesis Outputs

Glucose and Oxygen

Cyanobacteria

Photosynthetic prokaryotes (no nucleus) that produce oxygen as a byproduct.

Why is cyanobacteria useful as symbionts?

Produced oxygen, and fixed nitrogen gas, which led to the synthesis of amino acids and nucleic acids

Endosymbiotic Origin of Mitochondria and Chloroplasts?

Cyanobacterium was engulfed, leading to the development of chloroplasts

What are plants?

Photosynthetic eukaryotes with chloroplasts with two outer membranes, resulting from primary endosymbiosis

What is the general outline of the primary plastid clade?

Red Algae

Contain cellulose walls

Only have Chlorophyll A (like cyanobacteria)

Chlorophytes

Streptophytes

1. A major clade of green plants that includes land plants and some green algae.

2. Known for phragmoplasts and plasmodesmata, oogamy, and apical growth

3. Not all of them exhibit oogamy, apical growth, or plasmodesmata (spirogyra)

Oogamy

When the gametes are in different size and form

Apical Growth

Occurs in the apical meristems, at the tips of the roots and shoots

Plasmodesmata

Channels that penetrate the cell walls of adjacent cells that allows the cells to communicate and pass on materials

What is a green plant?

1. Eukaryotes with chloroplasts developed from primary endosymbiosis

2. chloroplasts woth chlorophyll A and B

3. Store carbohydrates as starch

Is green algae the earliest branching green plant?

Yes, they mainly exist in marine or fresh water environments

Phragmoplasts

Help algae grow 3-dimensionally, fuse with plasmodesmata

Parenchyma

Basic tissue type in streptophytes with cells linked by plasmodesmata

Potential challenges for a terrestrial plant?

1. Dry, hot conditions

2. Lack of transport systems

3. No structural support

4. No method of dispersing reproductive cells

Mycorrhizae

Fungus which grows on plant roots, allowing the plant to abosrb more water and nutrients.

Sporopollenin

Protects spores against desiccation and decay

Accessory Pigments

1. Protect against UV radiation

2. Increase photosynthetic efficiency

Stomata

Closable openings that regulate gas exchange

Waxy Cuticle

Waxy coating that slows water loss

Bryophytes

1. Nonvascular land plants, includes liverworts, mosses, and hornworts

2. No true roots, stems, or leaves (need to stay small to transport water and nutrients)

3. No strong support tissue

4. Have signaling proteins that are involved in desiccation tolerance

Mosses

1. Erect leafy gametophytes

2. Hydroids allow water to move

3. Sporophyte attached to gametophyte and dependent on it

4. Unbranched sporophyte

5. Stomata on capsules

6. Peristome teeth aid dispersal

Liverworts

1. Green flat gametophytes

2. Growth occurs at the apex of the plant

3. Sporophyte remains attached to the larger gametophyte

4. Most can reproduce asexually and sexually

5. No internal water conduction

6. No true stomata

Hornworts

1. Sporophytes look like small horns

2. Cells contain one chloroplast

3. Sporophyte grows from a basal region

4. Have a symbiotic relationship with cyanobacteria

Antheridia

Produces motile sperm

Archegonia

Produces egg cell and houses embryo after fertilization

Sporangia

Produces haploid spores through meiosis

Life Cycle of Nonvascular Land Plants

1. Spores grow, producing haploid (1n) multicellular gametophytes, which make gametes by mitosis in gametangia (either in antheridia or archegonia)

2. Eggs are fertilized by sperm to form diploid zygotes

3. Diploid zygote develops by mitosis into an embryo, which grows into a diploid plant

4. The diploid plant is called the sporophyte, which will then form spore-producing sporangia

5. Cells in sporangia produce haploid spores by meiosis

Liverwort Sporophytes

1. Has a stalk (seta) and capsule (the sporangium)

2. Sporophyte is attached to the gametophyte and physiologically dependent on it

3. Stalk elongates rapidly

Elaters

Assist in spore dispersal by flexing in response to changes in humidity

What clade has the sporophyte phase being dominant in the lifecycle?

Tracheophytes

Heterosporous Life Cycle

1. Megagemtophyte (n) → Egg (n) → Fertilization → Zygote (2n) → Embryo (2n) → Sporophyte (2n) → Megasporangium (2n) → Spore Mother Cell (2n) → Meiosis → Megaspore (n) → Megagametophyte (n)

2. Microgametophyte (n) → Sperm (n) → Fertilization→ Zygote (2n) → Embryo (2n) → Sporophyte (2n) → Microsporangium (2n) → Spore Mother Cell (2n) → Meiosis → Microspore (n) → Microgametophyte (n)

Homosporous Life Cycle

Gametophyte (n) → Antheridium and Archegonium → Sperm and Egg → Fertilization → Zygote (2n) → Embryo (2n) → Sporopphyte (2n) → Sporangium (2n) → Spore Mother Cell (2n) → Meiosis → Spore (n) → Gametophyte (n)

Microphylls are found in what lineage?

Lycophytes

Synamorphies between Euphyllophytes and Leptosporangiate ferns

Megaphylls v Microphylls

1. Microphyll → one vein

2. Megaphyll → multiple veins

Life Cycle of a Fern

1. Mature gametophyte has archegonium in the top of the heart shape and antheridium on the bottom

2. Antheridium releases sperm into water and the sperm fertilizes the egg, creating a diploid embryo

3. The sporophyte holding the embryo grows and matures, and the sporangium goes through meiosis and releases spores.

4. Spores germinate and grow into a gametophyte

Leptosporangium

Single cell thick

Annulus

Ring of cells in the sporangium of ferns that help distribute spores

Are Bryophytes a clade?

Yes

Are tracheophytes (vascular plants) a clade?

Yes

Vascular Plants

Branched sporophyte that is independent of the gametophyte at maturity

Having a tall sporophyte can cause a plant to evolve new transport methods?

True

How long ago do vascular plant fossils date back to?

420 MYA

When does major diversification occur?

360-300 MYA

When do the first forests appear in the fossil record?

390 MYA

Lycophytes

1. Independent sporophyte and gametophyte generations

2. Dichotomous branching roots

3. Sporangia in strobili

4. Have microphylls arranged spirally on the stem

Strobili (strobilus)

Cluster of sporangia

Are most vascular plants heterosporous?

Yes

Heterospory

1. A megaspore develops into a female gametophyte (megagametophyte)

2. Microspores develop into male gametophytes (microgametophytes)

3. Found in lycophytes, ferns, seed plants

Homospory

1. A plant develops archegonium and antheridium

2. Found in bryophytes, lycophytes, and most ferns

Euphyllophytes

All vascular plants except lycophytes

• AKA true leaf plants

Euphyllophyte Synamorphies

1. Megaphylls

2. Multiflagellate sperm

3. Roots with endogenous branching

Monilophytes consist of (2)

Horsetails and Ferns

Monilophytes

1. Sporangia are on a stalk in clusters called sori on the undersides of leaves

2. Terrestrial

3. Require liquid water for movement of sperm

4. Gametophyte is small and short-lived

5. Sporophyte can be large and live indefinitely

Apoplastic Route

1. Cell walls and intercellular spaces

2. Continuous meshwork of cellulose in cell walls

3. Water and solutes never cross a membrane

Symplastic Route

1. Continuous cytoplasm of living cells connected by plasmodesmata

2. Plasma membranes control movement of water and ions

Transpiration-Cohesion-Tension Model

1. Water evaporates through the leaves, creating tension (negative pressure in the leaves)

2. The tension pulls the water up the xylem, and is assisted by cohesion and adhesion

Does the process of transpiration itself require energy from the plant?

No because the process is controlled by evaporation

Pressure Flow Model of Phloem Movement

1. Sugars are produced in the leaves, and stored in roots or fruits. Sucrose is actively transported into companion cells and diffuses into sieve tubes

2. Increased pressure of water in the sieve cells from osmosis forces the sugars to move down the phloem, where sugar concentration is lower

3. Once at the sink, sucrose moves out through facilitated diffusion and water moves back to the xylem

Vascular Tissue

Specialized system of pipes for conducting water and minerals from the roots to the top (xylem) and conducting sugars from the leaves to the roots (phloem)

Xylem Cells

Functional xylem tissue is dead bc only the cell walls remain

• Tracheids and vessels belong in the xylem

Do root hairs do most water absorption?

Yes

Where is the area of growth in the roots?

The root tip

If the stomata is open..?

1. CO2 can come in

2. O2 can leave

3. H2O evaporates (transpiration)

If the stomata is closed…?

1. CO2 can be depleted by photosynthesis

2. O2 can accumulate, inhibiting photosynthesis

3. H2O is trapped in leaf

Do stomata control the flow of water through the xylem?

Yes

Does the movement of phloem sap require living cells?

Yes, the phloem has sieve cells

• sugar moves through the cell membranes of these cells

Does the Pressure Flow Model require energy from the plant?

Yes because it depends on active transport

Synamorphies of Seed Plants

1. Production of seeds

2. Pollen grains for male gametes

3. Vascular tissue

Apical Meristem Function

Create new cells that extend the roots and shoots of plants

Primary Growth

Elongation of the growing tip of a plant by the apical meristem

Secondary Growth

1. Consists of Vascular Cambium, which produces secondary xylem and secondary phloem

2. Consists of Cork Cambium, which sometimes becomes the outer bark

3. Increases the diameter of a plant

Is wood secondary xylem?

Yes

Why do trees have rings?

Because wood is the accumulation of secondary xylem

Cork Cambium

Produces waxy-walled protective cells

Cycads

1. Pinnate leaf structure

2. Short woody trunks

3. Dioecious

   • Females have seed-bearing leaves

   • Males have strobili

4. Sperm have flagella

Conifers

1. Cones contain

• megastrobilus → female cone, seeds protected by woody scales

• Microstrobilus → male pollen-bearing cone

2. Sperm does not have flagella

3. Simple leaves

4. Wind pollinated and seed dispersal by animals

Megastrobili

Female cone in gymnosperms that produces seeds

Microstrobili

Male cone in gymnosperms that produce pollen

Dioecious Plants

Plants that have male and female flowers on separate plants

Monoecious Plants

Plants with both male and female flowers on the same plant

What is the microgametophyte of seed plants?

Pollen grains

Which lineages produce flagellated sperm?

Every lineage except for gymnosperms and angiosperms

Spermatophytes

Vascular plant clade sister to the monilophytes

• AKA seed plants

Are gymnosperms a clade of seed plants?

Yes

Gymnosperms

1. Do not form flowers or fruits

2. Ovules and seeds are not protected by ovary or fruit tissue

3. Have only tracheids in the xylem

Gymnosperm Groups (2)

Cycads and Conifers

Are gymnosperms dioecious or monoecious?

Dioecious

Are conifers monoecious or dioecious?

Monoecious

Life Cycle of a Pine Tree

1. Megasporocyte (2n) in the megasporangium undergoes meiosis → Megaspore (n) with pollen chamber and micropyle → Pollen grain enters the pollen chamber and fertilizes the egg → Zygote (2n) → Seed (2n) → Megastrobilus (2n) → Seed → Sporophyte (2n) → Megastrobilus or Microstrobili (2n)

2. Microstrobili (2n) in the microsporangium undergoes meiosis → Microspores (n) → Pollen grain (n) → Fertilizes egg after going through the pollen tube

Gymnosperm Female Function

1. Ovule originates as megasporangium

2. 4 haploid megaspores formed by meiosis, 3 die

3. Remaining megaspore grows by mitosis into megagametophyte

4. Archegonium forms and produces a pollen chamber and egg cells

5. Pollination droplet develops when ovule is ready for pollination

6. Sperm are released and fertilize egg

7. Zygote grows into embryo while the megagametophyte grows to fill megasporangium and concentrates nutrients for embryo

Synamorphies of Angiosperms

1. Xylem contains vessels and tracheids

2. Flowers

3. Fruits

4. Ovules and seeds enclosed in a carpel

5. Germination of pollen on a stigma

6. Double Fertilization

7. Nutritive tissue called Endosperm

Pollen

1. Each anther sac is a microsporangium

2. 4 haploid microspores formed by meiosis from each diploid microspore mother cell

3. Each microspore undergoes mitosis and forms 2-cell pollen grain

4. One cell is the generative cell which divides by mitosis to form 2 sperm cells

5. Other cell is the tube cell which forms the pollen tube

How do different layers in gymnosperm and angiosperm seeds represent different generations?

1. Gymnosperms are naked and enclosed without a seed

2. Angiosperms are enclosed in a fruit

Angiosperms

1. Seed plants that have reproductive organs in flowers and seeds enclosed in fruits

2. Vascular plant clade sister to the gymnosperms