Evolution of Plants

A. Characteristics of Plants 1) Eukaryotes with a nucleus 2) Multicellular with tissues specialized cells that work together 3) Cell wall made of cellulose 4) Autotrophs/photosynthetic 5) Have 2 different body forms (alternation of generations)

B) 1n vs 2n 1) 1n = haploid (half #chromosomes) a) gametes are 1n (egg & sperm) b) gametes are made by meiosis 2) 2n=diploid (full set of chromosomes) a) zygotes are 2n b) sperm fertilizes egg to make zygote c) 1n egg + 1n sperm = 2n zygote

C. Meiosis vs Mitosis 1) meiosis: cell division to make gametes a) only done for sexual reproduction b) one cell divides into 4 cells c) each cell has ½ the DNA of the parent cell 2) mitosis: cell division to grow a) each cell has the same amount of DNA as the parent cell b) one cell divides into 2 cells

D. Body forms in the two Generations 1. gametophyte=plant body,makes gametes A. gametes are reproductive cells B. egg and sperm C. each has ½ the DNA needed to make an embryo 2. Sporophyte = plant body makes spores A. Spore = reproductive structure protected by hard wall. B. germination = plant breaks wall of spore and begins to grow.

Plant Evolution

E. Vocab 1.Spores (1n) germinate and grow into gametophytes (1n) 2. Gametes(1n) fuse and grow into sporophytes(2n) 3.Sporophytes(2n) make spores(1n) by Meiosis (2n 1n) 4.Gametophytes(1n)make gametes (1n) Mitosis (1n 1n)

F. Charophytes: Link plants & algae 1.no alternation of generation a. so not plant b. live in water but can dry out 2.similar to plants a. cell walls made of… cellulose b. Chloroplasts

G. First True plants (w/ alt. gen.) evolved 50 mya 1.Primitive plants have: a) swimming sperm b) main generation = gametophyte c) sporophyte ON gametophyte d) no veins (non-vascular) e) no seeds f) these traits are like algae

2. 50 mya =Ordovician Period a. Ozone layer had finally formed b. ozone protects from U-V radiation c. allowed life to move onto land 3. Advantages to life on land a. Higher CO2 concentration b. More direct sunlight c. Soil nutrients d. No herbivores

4. Challenges to Life on Land a. Desiccation (drying out) i. got a wax coating = cuticle b. Gravity i. water holds up aquatic plants ii. Air offers no support iii. Early plants lay on ground 5. Earliest plants = Bryophytes a. Hornworts b. Liverworts c. Mosses

period3. Called Bryophytes

H. First Vascular plants 1.have veins to transport H2O & sugars 2. called Rhyniophytes 3. only stems a. no roots b. no leaves 4. no seeds 5. only fossils (paleobotany) 6. evolved into 2 modern groups of plants

I. Extant (living) vascular plants 1.Seedless: Lycophytes, horsetails & ferns a.New traits i. stronger cell walls -. grow up off the ground (upright growth) -. Reach light ii. rhizomes = underground stems iii. First dominant sporophyte (sporophyte larger than gametophyte)

b.primitive traits i. swimming sperm (so need damp habitat) ii. no seeds

Lycophyte sporophytes Ground pines Club moss

Horse tails sporophytes Equisetum Scouring Rushes

Ferns sporophytes sori full of spores Gametophytes microscopic

C. Carboniferous Period: i. coal deposits ii. Seedless vascular plants tall as trees iii. Δ sea levels dry & flood swamps iv. Layers of dead plants build up faster than they decompose

2. First Seed Plants = gymnosperms a. Gymnosperm = naked seed(no fruit) b. Conifers = seeds in cones c. appear in Carboniferous period

d. seeds = adaptation to dry e. seeds made by ovules (eggs) fertilized by sperm carried by pollen (not swimming sperm) f. Pollen = freedom from water, it is carried by wind so can disperse on land

G . Advantages of Seeds i. Multicellular vs spores unicellular ii. Have stored energy (starch/oil) * allows delayed germination *enhanced early growth iii. Protective coating over embryo iv. May have dispersal aids

3. More modern seed plants =Angiosperms a. Angiosperms = flowering plants b. Seeds form in Ovary of flower c. Ovary may grow into a fruit d. now 90% of all plant species e. Co-evolved with pollinators

4. Flowers a. Sex i. Male flowers only make pollen ii. Female flowers only make ovules iii. Perfect flowers have both (hermaphrodites) b. Complete flowers i. Must have all flower parts (none missing) ii. Must be perfect (both male and female) ii. Imperfect flowers are missing parts

Male flower parts

Female flower parts