LECTURE 24- Tree of life, biomes, and life cycles

what are terrestrial biomes determined by

temperature, precipitation, latitude and elevation

what are aquatic biomes determined by

light and nutrient availability

Rainforest characteristics

• consistent temperature above freezing

• high consistent rainfall

• dominant in woody species

• high species diversity

• lots of light competition

• lots of epiphytes and vines

what are the five layers of a rainforest

• emergent layer

• canopy layer

• understory

• shrub layer

• ground layer

tropical deciduous forest characteristics

• warm consistent temperature

• consistent temperature with seasonal dry periods

• dominant in deciduous species

• lower species diversity than rainforest

Savannah characteristics

• warm/dry zone

• insufficient rainfall for dense forests

• dominant in grasslands and shrubs/short trees

• deciduous trees occur in drier seasons

• large grazing animals present

Desert characteristics

• multiple different temperatures (anually above freezing)

• Hot deserts = lower latitudes. Cold deserts = higher latitudes

• Globally above 30 degs north and below 30 degs south latitudes

• little rainfall

• specialised vegetation to conserve water and protect plants from weather

• cacti and succulents are common

grasslands characteristics

• Temperate zones with seasonal climate

• Adequate rainfall to support diverse species (not trees)

• dominant in grasses and other annual/perennial species

Temperate deciduous forests characteristics

• mostly in northern hemisphere

• seasons occur and continuous rainfall

• summer = warm temps. winter = snow cover and freezing temps

• dominant in deciduous trees

• temp change causes changes in deciduous plants

• Species diversity isn’t as high

Temperate mixed & conifer forests

• Similar to deciduous forests

• colder with more snow

• Nutrient poor and water logged soils that cause swamps

• trees have adaptations for the climate (e.g. buttresses)

• mix of deciduous and evergreen species

• Species diversity not as high

Mediterranean Scrub (Heathlands) characteristics

• distinct shrub communities

• hot and dry summers

• moist and cool winters

• Some deciduous or evergreen species

• Fire-adapted species

• Fire may stimulate seed germination or releasing seeds from fruits

Taiga/boreal forests

• Winter = short, very cold days

• Summer = long days (short growing season)

• sufficient precipitation for tree growth

• diverse in moss/lichens

• diversity lower due to acidic soil

• includes permafrost. Shallow area for root growth

Arctic tundra characteristics

• mostly above arctic circle

• treeless zone and little precipitation

• moisture derived from frozen surface

• dominant in evergreen species (grasses, mosses, dwarf trees)

• long summers. completely dark in winter

what is the tree of life

phylogeny that represents history of a group of organisms

what characteristic to ferns, angiosperms and gymnosperms share

true leaves

what trait do angiosperms and gymnosperms share

seeds

why is studying the tree of life important

Being able to compare and contrast the similarities and differences of plant groups on understand their complexity

what is a ploidy level

number of chromosome sets present in a cell, structure or organism

• 2n= diploid (two chromosome sets)

• n= haploid (one chromosome set)

what are the 3 types of life cycles

• Zygotic meiosis

• Genetic meiosis

• Sporic meiosis

what plants exhibit sporic meiosis

All true plants and some algae

basic sporic life cycle structure

1. sporophyte (2n) produces spores (n)

2. spores grow into haploid gametophytes (n)

3. gametophytes produce haploid gametes (n)

4. gametes fuse and make a zygote (2n)

5. zygote grows into sporophyte (2n)

what alternates during a sporic life cycle

alternates between sporophytic diploid stage and gametophyte haploid phase

what are isogamy gametes

gametes look the same and have flagella (motile)

what are anisogamy gametes

gametes are dissimilar; one is larger than the other. both have flagella (motile)

what are oogamy gametes

• one gamete is large with no flagella (egg)

• one gamete is small and motile (sperm)