BIOL113 Plant Diversity

Advantages of living in a terrestrial environment

Less predation, more sunlight, more CO2, soil rich in nurtients

Disadvantages of living in a terrestrial environment

Lack of structural support, lack of water

Four traits that characterise plants

alternation of generations, cuticle, stomata, meristem, walled spores

How does alternation of generations relate to colonising terrestrial environments

Allows for reproduction and survival

How does the cuticle relate to colonising terrestrial environments

helps maintain moisture and prevents drying out

how does the stomata relate to colonising terrestrial environments

helps control gas exchange

how does the meristem relate to colonising terrestrial environments

allows roots to grown downwards for soil and nutrients and leaves upwards towards light

how do walled spores relate to colonising terrestrial environments

strong cell wall around spores allows for structure

when did prokaryotes evolve

around 3.5 BYA

When did eukaryotes evolve

around 2.8 BYA

When did multicellular eukaryotes evolve

around 1.3 BYA

when did first plants evolve

0.5 BYA

what is taxonomic classification

allows us to name things and see what is related to what. Understanding the relationship and the evidence

What is polytomy

a node on a phylogenetic tree where two or more lineages emerge from a single ancestral node

Names of taxonomic classification

Domain, kingdom, phylum, class, order, family, genus

what are plants most closely related to

The charophytes

non-vascular plants

bryophytes

Phylum hepatophyta

Bryophyte, Liverworts

Phylum Bryophyta

bryophyte, mosses

Phylum Anthocerophyta

bryophyte, hornworts

Phylum Lycophyta

Seedless vascular plant, lycophytes, club mosses

Phylum monilophyta

seedless vascular plant, monilophytes, ferns

vascular plants

gymnosperms

flowering plants

angiosperms

Phylum antophyta

angiosperm phylum

Clade

monophyletic group (ancestral species and descendants) all member groups are more closely related to non-member groups than other member groups

Grade

paraphyletic group (ancestral species and some but not all descendants) some member groups are more closely related to non-member groups than other member groups

Character

Refers to a trait or species

Character state

the value of a trait

Plesiomorphy

primitive character state, inherited from a common ancestor

Ancestral state

the value of a trait in an ancestor

Apomorphy

derived state

synapamorphy

derived character states shared between lineages

Derived state

a feature that evolved in specific in a specific lineage, appearing in the most recent common ancestor and its descendants

Bryophyte life cycle

Alternation of generations, haploid generation is sporophyte (meiosis), diploid generation is gametophyte (mitosis), female structure is archegonia, male structure is antheridia, gametophyte is dominant

Hepatophyta

No stomata, sporophytes are small, seta present, small pores on surface of thalli (allow gas exchange), thalloid and leafy liverworts are two growth forms

Anthocerophyta

Thalloid, stomata present, leaflet structure, seta absent, sporophytes (relatively large) only have stomata

Bryophyta

Leafy, stomata present only in sporophytes, sporophytes relatively large, seta present

Xylem

moves water and nutrients through the soil up the plant to leaves and stems, thick cell walls, cell dead at maturity

Phloem

transports water and photosynthates from leaves to roots, thinner cell walls, cells dead at maturity

Lifecycle of seedless vascular plants

sporophyte (diploid) is dominant, spore production occurs in sporangium, haploid spore released from sporangia, these land and germinate and grow in haploid generation (gametophytes), sperm cells are motile and have flagella and swim to egg (requires water)

Ancestral character states of seedless vascular plants

Seeds absent, sperm with flagella (so they can swim)

Derived character states of seedless vascular plants

Vascular system, free living system, dominant sporophyte stage, true roots (not rhizobia), leaves, sporophyll (modified leaves that bear sporangia)

Homosporous production

produces one type of spore that is the same size

Heterospore production

produces two type of spores, seperate male and female spores (microspores and megaspores),

Dermal tissue

surface of the plant, epidermis (stomata and cuticle), periderm (outer layer or woody tissue such as bark)

Vascular tissue

xylem, phloem

Ground tissue

involved in storage and photosynthesis.

Meristematic tissue

where cells divide

Primary growth

increase in length

Secondary growth

increase of width

Meristems asscioated with the tip of the shoot apical meristem

shoot apical meristem

Meristem associated with root

root apical meristem, apical meristem as tip of each root

Meristems associated with secondary growth

Lateral meristems, vascular cambion, cork cambion

Apical buds

extension of stems and branches, new leaves

Axillary buds

new branches

root tips

new roots, extension of roots

Root cap

protects root as it goes through soil, small layer of cells, caps the meristem, sense where things are/ direction of growth

Meristem

site of cell division

Elongation zone

Cells undergo considered elongation, this drives root tip through soil

Maturation zone

Once cells stop elongating they mature, root hairs develop which help increase the rate of diffusion due to large surface area. Cell division within the meristem gives rise to cell files

Primary growth in stems and branches

shoot apical meristem is enclosed by folded leaf primordia this protects meristem and newly formed leaves cluster around it

Vascular system in roots

vascular tissue is central, xylem tissue in edicots is arranged in a star pattern, endodermis is outer layer of vascular tissue or is the inner layer of ground tissue pericycle is located inside of this

Vascular system in stems

Discrete vascular bundles form a ring around the periphery of the stem, xylem has thick cell walls and is on the inside of the stem, phloem has much thinner cell walls

vascular system in leaves

discrete vascular budnesl contain both xylem and phloem, xylem typically occurs on the upper side while phloem on the lower side, this results from the organisation of the xylem and phloem within the stem and petiol.

Leaf polarity

xylem on upper side, phloem on lower side, stomata more common on the lower side than the upper side, palisade mesophyll on the upper side and spongy mesophyll on the lower side.

Cell types in the xylem

tracheiads (narrow and long and present in all vascular plants), vessel elements (wide and short) present in angiosperms and some seedless vascular plants

Cell types in phloem

sieve cells (present in all seedless vascular plants and gymnosperms), sieve tube elements (present in angiosperms)

What does the vascular cambion do

increases width, allows development of wooden tissue

gymnosperm seeds

seed coat (maternal 2n), embryo (offspring, 2n), nutrient tissue (female gametophyte, n)

angiosperm (monocot) seed

seed coat tissue (maternal, 2n), embryo (offspring, 2n), endosperm (nutrient tissue, 3n)

advantages of seed

food supply, dispersal unit, protective coat

Advantages of pollen

protective coat, independence of water for transport

gymnosperms

gametophytes are microscopic and depened on sporophytes for growth, sporophyte is diploid and dominant

Angiosperms

gametophytes are microscopic and dependent on sporophytes for growth

Monilophytes

gametophyte is free living and independent even if it’s reduced

bryophytes

in mosses and other bryophytes the sporophyte is reduced and dependent on the gametophyte for its growth

Heterospory

formation of 2 different types of spores, microspores produce male gametophyte and megaspores produce female gametophyte

endospory

retention of the gametophyte within the parent plant, female gametophyte does not germinate from the megaspore but remain surrounded by spore wall

the integument

cell layer that encloses the megasporangium, not present in ancestral state but is present in revived

2 linearges of seed plants

gymnosperms (naked seed) and angiosperms (covered seed)

gymnosperm lineages

cycadophyta, ginkgophyta, coniferophyta, gnetophyta

diagnostic characteristics of gymnosperms

seeds not enclosed in carpel, sporangia in gymnosperms are organised in cones, ovuliferous scale is a leaf, pollen forms in sporangia (microsporgangia), layer of tissue called integument formed protective layer over ovule, motile sperm, microphyll allows pollen grain to go through, time between pollination and fertilisation can be months or years

life cycle of gymnosperms

mature sporophyte makes seperate male and female cones (microspore and megaspore), microsporangia generates microspore through mitosis (pollen grain), megaspore development through meiosis, pollen grain is moved via wind to female cone, pollen will germinate

Diagnostic characteristics of cycadophyta

absence of lateral branches, compound leaves, circinate vernation (leaf unrolls), motile sperm cells, seperate cones as they are gymnosperms

Diagnostic characteristics of Ginkgophyta

simple leaves, motile sperm cells, female cones absent

diagnostic characteristics of coniferophyta

simple leaves, non-motile sperm cells

Diagnostic characteristics of Gnetophyta

presence of vessels (special xylem cells), non-motile sperm

Calyx

made up of structures called sepals on outside of flower

Corolla

flower petals

Perianth

Calyx and corolla

Stamens

male component of flower is made up of anther and filament

Capels

female component made up of stigma, style and ovary

4 rings of tissue in flowers

calyx, corolla, stamen, carpel

variation of flowers

size, colour, shape, number of floral parts, presence of absence of floral parts, female or male components (imperfect) or male and female components (perfect)

Radially symmetric

actinomorphic, can rotate around and has multiple points of symmetry

Bilaterally symetrcis

zygomorphic, can fold it but can’t rotate it around

Determinative shoot

once flower has grown shoot doesn’t grow any further

Where does pollen form in angiosperms?

anthers

What is an anther made up of

two thecae