History of Life on Earth and Eye Evolution Timeline
Biosphere
Cells: Basic Form Of Life
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biodiversity
the variety of life forms that occur on earth
- species diversity variety of species
- genetic diversity genetic variety in species
- ecosystem diversity variety of ecosystems in an area
BIODIVERSITY IN SOUTHERN AFRICA
- South Africa has the third highest level of biodiversity in the world because of the
unique physical characteristics
- largest part of country is on a high-lying plateau, between two oceans
- Indian Ocean is on East Coast, warmed by Mozambique/Agulhus current
- Atlantic Ocean is on West Coast, cooled by Antarctica/Benguela current
- the oceans, winds and topography create bright green forests and subtropical
savannahs on the east coast, which gradually turn into semi-desert on the west coast
Indigenous species
Occur naturally in a particular country or region
Exotic/Alien species
Do not occur naturally in a particular country or region, but have been brought there
from another country or region by mistake or deliberately
Endemic Species
Only occur in one country or region and nowhere else in the world. SA has a large
number of endemic species; many are endangered or critically endangered. Eg: Cape
Sugarbird, Riverine Rabbit, Disa Plant
HOTSPOTS
High degree of biodiversity as well as large number of endemic species that occur there
The Cape Floral Region
World Heritage Site (UNESCO). Richest in plants and provides exceptional value to
humanity.
- 0,05% of earth surface
- contains about 3% of worlds plant’s species
- 70% of 9 600 plant species are endemic
- eg. Cape sugarbird, geometric tortoise
,Succulent Karoo
- 40% of 5 000 higher plant species are endemic
- 18% are endangered
- eg. Halfmens, Lizards, Tortoises, Scorpions
Maputaland-Pondoland-Albany
East coast of South Africa and considered the temperate forest with the largest tree
kingdom. Most grasslands and forests are being threatened by industry and farming.
- home to 600 tree species
- Strelitzia reginae is endemic to region
classification
living organisms are divided into groups and subgroups according to similarities and
shared classifications
Classification became more complex as scientists learned more about the structure of
cells, microorganisms, evolution, genetics and molecular body
Two-kingdom system
1758, Carl Linnaeus, classified organisms into two
, - Linnaeus developed a hierarchical system of classification, where seven
categories (taxa) under each Kingdom are used
- categories are based on shared physical properties within each group
- classification starts at Kingdom, and each classification level becomes more
specific
A kingdom is subdivided into phyla for animals, but in plants the term division is used
Five-kingdom System
- as more information was obtained, two-kingdom was
expanded into five-kingdom
- Robert Whitaker proposed the five-kingdom
- following criteria are used to classify:
body structure:
unicellular/multicellular/colonies
cell structure: presence/absence of a nucleus; organelles (chloroplasts)
composition of cells: cellulose/chitin/no cell wall
motility: mobile/immobile
mode of nutrition: autotrophic/heterotrophic
method of reproduction: binary fission/asexual/sexual
PROKARYOTES AND EUKARYOTES
Divided according to their cell structure
Divided according to their cell structure
PROKARYOTES
EUKARYOTES
Prokaryotes
- organisms with cells that don’t have true nuclei
- DNA is not enclosed by nuclear membrane and occurs fee in the cytoplasm
- no true organelles occur in the cytoplasm
-Monera (bacteria) are prokaryotes
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