Download - UNIT 3 - EVOLUTION
UNIT 3 - EVOLUTION
• 3 ½ - 4 weeks … test around Nov. 23rd • Evaluation:
– 2 Quizzes, Written Test– Ind. Study Work … working in library or on
own
Adaptation & Variation
Extinction• To completely
disappear from Earth• Results when species
either lack diversity and/or the ability to change within their environment
• Eg. Dodo bird, etc.
Adaptations• Helps an organism
survive & reproduce• Can be structural,
behavioural or a physiological process
Adaptations
1. Structural• Too many to name
– Owls (talons, eyesight); sharks (sensory organs, teeth, graceful swimmers); bats (sonar); humans (brain, bipedal, thumbs), etc.
• Includes camouflage (stick insect, octopus…)
Mimicry
• A special structural adaptation• Harmless creatures posing as harmful
species in either colour or structure• Tricks predators into believing the critter is
untasty• Eg. Viceroy butterfly, king snake
Mimics
Adaptations
2. Behavioural• Things that animals
do, not what they have
• Eg. Meerkats standing, bird calls, migration,
Japanese honey bee adaptation
• Video: “Hornets from hell”
Adaptations
3. Physiological• Hibernation
– Bears can overwinter when food is scarce; ground squirrels can avoid harsh winters
• Tanning• Lactic Acid
fermentation (low O2)
How do Adaptations Develop?• Gradual, accumulative
changes over generations• Random, heritable
mutations in DNA• Variations → differences
between individuals (structural or physiological)
• Not all variations become adaptations
African Cichlids
Interactions with Environment
• Very important to adaptation & variation• Climates change; floods, droughts and
famines occur• Human activities – deforestation,
agriculture change landscapes• Unimportant characteristics may
eventually become crucial for survival if things change
Saguaro cactus• Fleshy stem holds water• Most roots < 15cm deep
but cover huge area• Can absorb 750 L of water
in a single storm• Leaves reduced to spines
to reduce transpiration rate• Spines also ↓ predation• Stomata only open at night
Variation to Adaptation
The English Peppered Moth• Light peppered colour and black• Historically black was rare – lichen on
trees in England was light coloured and moths were easy targets for birds
• Industrial Revolution killed lichen and put soot on trees; 50 years later 95% of Manchester moths were black
English Peppered Moth
Pre-industrial revolution Post-industrial revolution
Questions
1. Sharks have an excellent sense of smell. Is this a variation or an adaptation?
2. A black and yellow insect buzzes around you, causing you to freak out. When it lands you see that it is only a fly. What is the fly’s adaptation and explain the advantage.
3. When could genetic variation have no significant effect on a species’ survival?
Mutations
• Changes in genetic material (DNA)• New alleles = genetic variation• Eg. Your DNA has about 175 mutations
compared to your parents’ • Could be harmful or beneficial• In somatic cells → tumour• In gametic cells → may be passed on
Selective advantage• A genetic advantage
of one organism over its competitors
• Helps it to survive changing environmental conditions
• Eg. Water flea surviving in warmer water temperatures
Antibiotic Resistance
• Staphylococcus aureus (bacteria) can reproduce every 30 minutes
• Adaptation can occur very quickly• Treatment of Staph. Infections can be
inhibited by the adaptive bacteria• Populations of bacteria with the new allele
can create antibiotic resistance