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Life Science Grade 8. Chapters 5, 18, 19, 22 . Chapter 5. Heredity. What is Genetics?. Heredity : passing of traits from parents to offspring Alleles : different forms a gene may have for a trait Genetics: the study of how traits are inherited through the actions of alleles - PowerPoint PPT Presentation
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LIFE SCIENCE GRADE 8
Chapters 5, 18, 19, 22
Chapter 5
Heredity
What is Genetics?
• Heredity: passing of traits from parents to offspring
• Alleles: different forms a gene may have for a trait
• Genetics: the study of how traits are inherited through the actions of alleles
• Purebred- organism that always produces the same traits in its offspring
The Father of Genetics
Gregor Mendel (Austrian Monk born in 1822)
Experimented with garden peas– Quick germination– Quick growth– Easily observable traits
Mendel’s Experiments
• Mendel cross-pollinated purebred tall plants with purebred short plants
– He pollinated the plants himself!
– Results: tall plants crossed with short plants produced tall plants• it seemed as though the short trait had
“disappeared”
Dominant & Recessive Factors
• Mendel called the tall plants “dominant”• The tall “covered up” the short• Dominant – tall
• He called the form that disappeared "recessive”
• Recessive- short
What happened to the recessive (short) form?
Mendel’s Experiments
• Next, Mendel allowed the tall plants to self-pollinate
• Then, he collected the seeds from these tall plants & planted them
• RESULT: for every 3 plants tall, there was 1 short plant (3:1 ratio)– He saw this 3:1 ratio often enough to know that
the probability was great– He would get the same outcome each time
Using A Punnett Square
Punnett Square: used to predict results
Dominant Allele = Capital Letter (G)
Recessive Allele = Lower Case (g)
Using a Punnett Square (con’t)
• Homozygous- organism with two alleles that are identical for a trait (BB) (bb)
• Heterozygous- organism with two alleles that are different for a trait (Bb)
Using A Punnett Square (con’t)
• Genotype- genetic makeup• Phenotype- physical expression of the trait
Punnett Square Practice
Human Genetics
Investigating Inherited Traits Lab!
Chapter 18
Life & The Environment
Living & Nonliving Environment
• Biosphere- part of the earth that supports living organisms
• Abiotic Factors- nonliving physical features of the environment (air, water, soil, light, temp.)
• Biotic Factors- all of the living organisms in the environment (plants, animals, etc.)
Characteristics of Populations• Population Density: size of a population occupying
an area of a specific size
• Limiting Factor: any biotic or abiotic factor that restricts the number of individuals of a population
• Carrying Capacity: largest number of individuals an environment can support & maintain for a period of time
• Biotic Potential: number of individual each female of a population can produce under the best possible conditions
Predator-Prey Relationships• Predation: feeding of one organism on another
Symbiosis- any close relationship between 2 or more different species
(can be positive, negative, or neither)Symbiotic Relationship Description
Commensalism One partner benefits, the other is neither harmed nor helped in any way
Mutualism Both species benefit
Parasitism Benefits parasite and harms the host
Flow of Energy• All energy is derived from
the sun• Energy is transferred from
the sun through all tropic levels
Only about 10% of the energy available at each level is transferred to the next level.
Breakdown of the Energy Pyramid
The level of the energy pyramid consists of:– Producer (produces its own food)– Primary Consumer (feeds on producers)– Secondary Consumer (feeds on primary consumer)– Tertiary Consumer (feeds on consumers)
Food Chain Terms
• Producer: produces its own food• Herbivore: eats only plants• Carnivore: eats only meat• Omnivore: eats both plants & meat• Scavenger: feeds on dead remains of
plant/animal• Decomposer: breaks down organisms &
returns nutrients to the soil
Food Chain- animals that have a feeding relationship
Label the food chain above using “food chain terms”
Reminders: 1. food & energy are moving
from one organism to another
2. Arrows are drawn in the direction that energy flows
Food Web- linking together of food chains
Hydrologic (Water) Cycle
Evaporation from plants is called Transpiration
Nitrogen Cycle
Chapter 19
Ecosystems
How Ecosystems Change
Ecological Succession- process of gradual change from one community of organisms to another
Primary Succession• Primary Succession- begins in a place that
does not have soil– Lava flow, raised coral reef
Pioneer community- first community of organisms in this new environment– Hardy organisms that can survive drought,
extreme heat & cold, and other harsh conditions
Secondary Succession
• Secondary Succession- begins in a place that already has soil– Burned down forest, abandoned parking lot,
demolished building
Climax Community- has reached the final stages of ecological succession- May take hundreds or even thousands of years- Complex food webs
BIOMES
• Biome- large geographic areas with similar climates & ecosystems
• Factors that Effect Biomes:– Temperature– Latitude– Elevation– Precipitation
TUNDRA• Cold, dry, treeless region• “Cold Desert”
w/ little rain• Permafrost (permanently frozen soil)
Popular Species: lichen, moss, grass, small shrubs, muskoxen, reindeer, mosquitoes, birds, lemmings, Arctic hares, caribou
TAIGA
• Cold region of cone-bearing evergreens (pines, spruces, firs, hemlocks, cedars)
• Shrubs & grasses (lichen, moss)
Popular Species: plants from above, moose, black bears, lynx, wolves
TEMPERATE DECIDUOUS FOREST• You are here! (not at the mall)• Trees lose leaves every autumn– Beauty of Autumn
• Good soil = lots of vegetation
Popular Species: maple, oak, beech, birch, sycamore trees, deer, foxes, squirrels, mice, snakes, huge number of birds & insects
TROPICAL RAIN FOREST
• Found near the equator• Abundant rainfall & high temperature &
humidity• Unique plant & animal life • Lush, dense forest
Popular Species: snakes, lizards, frogs, parrots, toucans, cockatoos, humming birds, ocelots, peccary, jaguars, orchids, ferns, mosses, bromeliads
Layers of Vegetation
• Canopy- top of forest (leafy branches of trees)
• Understory- shrub layer
• Forest Floor (dark & moist)
GRASSLANDS
• Dominated by grass• Little rainfall (more than desert or tundra)• Grasslands are found on nearly every continent
Popular Species: kangaroos, wildebeests, zebras, meadowlarks, prairie chickens & dogs, bison
wheat, oats, barley, rye, corn (harvested here)
DESERT
• Driest biome on earth!• Less than 25 cm of rainfall yearly• Little plant life• Poor soil• Barren, Windblown
Popular Species: whitetail deer (largest population in world), sagebrush, cacti, lizards, iguanas, tarantulas, roadrunner, coyote
Adaptations of Desert Plants & Animals
• Adaptation- any characteristic an organism has that makes it better able to survive in its surroundings… adaptations are INHERITED
PLANTS: CactiSucculents
ANIMALS:
-Reduced spiny leaves
-Large, shallow rootsOr Fibrous Root System
- Waxy Outer Coating
- Rapid Germination
-Nocturnal
-Burrow deep in ground
-Large ears (release body heat)
-Store water in bodies
Chapter 22
Nutrients & Digestion
WHAT do you eat?
• Breakfast:
• Lunch:
• Dinner:
• Snacks:
WHY do you eat?
• To obtain energy for your body to carry out cell development, growth, & repair
NUTRIENTSNutrient- substances in foods that provide energy & materials for
cell development, growth, and repair
Carbohydrates Protein Fats/Oils Vitamins Minerals Water
Main source of energy for your body
Your body uses proteins for growthAmino Acids- building blocks of proteins
Provide energy & help body absorb vitamins
Needed to help your body use other nutrients
Regulate chemical reactions in your bodyElectrolytes
Enables chemical reactions to take place
Foods that contain the same nutrients belong to a food group
We have now moved toward the “My Plate” model…
Antioxidants
Antioxidants- substances that prevent other chemicals from reacting with oxygen– fruits & vegetables are known to contain antioxidants
that lower the risk of getting various diseases
Enzymes- Nature’s Chemists
Enzyme (AKA: “CATALYST”) substance that speeds a chemical reaction (without raising the
temperature)
*enzymes are not changed by reactions
Mechanical Digestion Chemical Digestion
Food is chewed & mixed in your mouth and churned in your stomach
Breaks down large molecules of food into smaller molecules that can be absorbed by cells
Small IntestineVilli- absorb nutrients into bloodstream
Large IntestineWhere it all ends!
Small & Large Intestine