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