This preview shows page 1. Sign up to view the full content.
Unformatted text preview: ic order) – both charophyte and charales as group names seem to be in dispute – fresh water – “pondweeds” – ~400 species • closest rela*ves of the land plants h[p://www.mlswa.org/
large_pics/narrow‐leaf_pondweed.JPG the Kingdom Plantae (taxonomic level = Kingdom) Note: chlorophytes are one group that is included in the “green algae” “green algae”, like “pro*sts” is no longer favored by taxonomists contains too many unrelated groups when we say “Plants”, we mean the clade of Land Plants Here, we will use chlorophytes and green algae interchangeably (we won’t talk about the other “green algae” groups) what is a plant? “Higher plants” includes most of the land plants you are familiar with, but also many you might not be familiar with To capture light, they use: Chlorophyll a Chlorophyll b Carotenoids Xanthophylls Advantages to plants of being on land • Advantages • Disadvantages • new, unused territory • escape from enemies, and disease • Bright, bright light • Diﬃcult to get nutrients – Rela*vely sterile environment • Need to support the body upright • Need to stay moist • Need protec*on from UV damage Plants need to stay moist Plants need to stay moist Problems the ﬁrst land plants needed to solve • Gerng resources without being able to move • Gerng resources to where they are needed in the plant body – the moving water of their former habitats was no longer present to do this work h[p://www.ncwildﬂower.org/index.php/image_galleries/Lake‐
Waccamaw‐Myrtle‐Head‐Savannah Gerng water to where it is needed Mosses are land plants but they do not have a vascular system They absorb nutrients through their surfaces Advantageous to: have a lot of surface area have structures that can store a lot of water h[p://www.na*vetreesociety.org/ﬁeldtrips/penna_cook_forest/
cookphoto/moss01_small.jpg Kingdom Plantae How did we get from Let's start at the beginning of the evolu3on of land plants... Charales Rhynia Mighty Oak land plants evolved from a clade of green algae that shared (synapomorphies): • Plasmodesmata, – connec*ons between cells joining their cytoplasm • branching growth from the apical (top) *p of the organism • embryos: egg is retained within parent organism – protec*on from desicca*on – egg becomes associated with addi*onal *ssues (embryo) h[p://users.rcn.com/
Junc*ons.html other important adapta*ons for terrestrial life • cu*cle (see previous slide) • gametangia – cases enclosing gametes • pigments to protect against UV damage (see previous slide) • spore (in large diversity of plant life cycles) walls are thick and contain sporopollenin protein – polymer – helps prevent desicca*on, rorng • mutualis*c associa*ons with fungi liverworts and hornworts • are nonvascular, no apical growth, thought to be basal to the clade consis*ng of mosses and vascular plants – basal = diverged anciently (at the base of the tree) rela*ve to other taxa early land plant *me line • ~500 mya the ancestral land plant evolves from a green alga species living in shallow freshwater • lycophytes (club mosses and related groups) and pteridophytes (horsetails, ferns, others) appear 409‐354 mya (Devonian period) • Forests of lycophytes, some 40m tall dominated during the Carboniferous period (360‐300 mya) – dominant land life form for ~200 my – became coal deposits in N. America, Europe, elsewhere h[p://archive.ﬁeldmuseum.org/
models_images/geo75400.JPG land plant fossil record • vascular plants fossilize be[er, appear in the fossil record before nonvascular plants • DNA evidence provides evidence that nonvascular plants predated vascular plants – this is the accepted view • ancient microfossils have cellular morphology similar to modern day liverworts Mosses...
View Full Document
- Spring '08