Plants and Animals How do Organisms Grow Growth

Plants and Animals How do Organisms Grow?

Growth �All organisms begin as a single cell. �In more complex organisms, like humans, the cells are specialized, meaning they have specific jobs. �When cells multiply, they produce exact copies of themselves so the new cells can carry on the same jobs.

Inside of the Cell �We know the nucleus is inside of each cell. �Inside of the nucleus are threadlike strands called chromosomes, which are made up of DNA. �The DNA in a cell determines the shape and function of the cell it is in.

Cell Division �The DNA also tells the cell when to divide. �When a cell divides, the DNA copies itself and each new cell has an exact copy of DNA in it. �This process of cell division is called mitosis.

Mitosis � Step 1: Chromosomes pairs are copied and split. (prophase) � Step 2: Chromosomes line up in the center. (metaphase) � Step 3: Chromosomes pull apart. (anaphase) � Step 4: The cell membrane pinches in the middle, splitting one cell into two cells. (telophase/cytokinesis) � The new cells have identical DNA to each other and to the parent cell.

Mitosis

Plants and Animals How do Organisms Multiply?

Regeneration �Regeneration is a form of tissue replacement. �in humans, regeneration is mostly used for healing wounds. �In other organisms, such as lizards and jellyfish, can completely “re-grow” limbs. �Starfish Regeneration

Fission �Fission is a simple cell division. �Unicellular organisms like bacteria and protozoa go through this process.

Budding �Budding: tiny buds form on the parent cell, and then the DNA copies itself in the bud. Eventually, the bud separates from the parent cell. �Yeast is unicellular fungus that uses this process.

Plants and Animals Life Cycles

Life Cycles �Life cycle: stages of life that almost all organisms go through. �Begins with a young organism going through a stage of growing and developing until it reaches adulthood. �Once an organism reaches adulthood, it is able to reproduce.

Direct Development �Direct development: young organisms grow larger, but maintain the same body structures until they are adults. �Spiders and earthworms are examples.

Metamorphosis �Metamorphosis: changes in shape or structure of an organism’s body from when they are young to when they are adults.

Incomplete Metamorphosis �Incomplete Metamorphosis: organisms that change from youth to adult in three stages. �Egg, nymph, and adult �Between stages they shed their outer skeleton: molting – allows for growth. �Cockroaches and grasshoppers

Incomplete Metamorphosis

Complete Metamorphosis � Complete Metamorphosis: organisms that change dramatically from youth to adult in four stages. � First stage: egg � Second stage: larva – lacks wings, looks diff. from adult; spends most of its time eating and storing energy. � Third stage: pupa - uses stored energy to break down larva body and produce adult body. � Final stage: adult – emerges from pupa stage; females can lay eggs and begin the cycle again. � Caterpillars and beetles

Complete Metamorphosis

Complete Metamorphosis �For a butterfly, the larva stage is when we see a caterpillar. The pupa stage is when we see a cocoon, or chrysalis.

Plants and Animals From Parents to Offspring

Inherited Traits �inherited trait: a characteristic that is passed on from parent to offspring. �Could be hair color, eye color, ear lobes, etc. �Behaviors can also be inherited; dogs are born with the instinct to be able to swim, humans are not.

Gregor Mendel �Gregor Mendel was a monk and scientist. �He studied pea plants and noticed that some grew tall and some stayed short, while other produced green peas and some produced yellow. �He wanted to experiment to find out why these changes happened, so he began crossbreeding, or mixing, different types of pea plants together.

Gregor Mendel �He began by crossing two tall pea plants. �The first generation produced 100% tall plants. �When these plants produced offspring, 75% were tall plants and 25% were short plants. �What do you think this could mean?

Gregor Mendel �Mendel made a hypothesis: he said that every trait is controlled by a set of factors. �Each organism receives one set of factors from the mom and one set from the dad. �The traits that an organism has depends on how these factors are passed on to them. �Therefore, Mendel guessed that the short factor must have been hidden somewhere in the first generation.

Dominant vs. Recessive Traits �Dominant trait: strong trait; will show in the offspring if they receive it from either parent. �Recessive trait: weak trait; will show in the offspring only if they receive it from both parents.

Genes �Gene: Mendel’s factors; contain DNA codes for all of an organism’s traits. �They are found on chromosomes, and each gene has a specific location. �The likelihood of certain genes being passed on can be calculated using a Punnett square.

Punnett Square �In a Punnett square, one side (top) represents one of the parents, and the other side (left) represents the other parent. �A dominant trait is represented with capital letters, and a recessive trait is represented with lowercase letters. �If you have one dominant and one recessive factor for the same trait, then it is one capital and one lowercase letter.

Punnett Square �Let’s say that brown fur is dominant for a rabbit (B) and white fur is recessive (b). �If the mother is dominant (BB) and the father is recessive (bb), what does that mean for the offspring?

Punnett Square �Since all of the offspring would be mixed (Bb), they would all have brown fur. �Remember, the recessive trait only shows if BOTH factors are lowercase. �Suppose a rabbit with mixed factors (Bb) mixes with a rabbit that was recessive (bb). What does this mean for their offspring?

Punnett Square �Since two of the offspring are mixed (Bb), those two offspring will both have brown fur. �The other two offspring are recessive (bb), so those two will both have white fur. �In other words, 50% will have brown fur and 50% will have white fur.

Plants and Animals Plant Parts – The Roots

Common Parts �Almost all plants have three main parts: �Roots �Stems �Leaves

Roots �Most roots act as anchors. �They also take in water from the soil through tiny parts called root hairs. �Roots can store excess food for plants.

Roots can adapt to their environment. �Desert roots spread far out but stay close to the surface so they can collect as much rain as possible. �Forest roots do not need to spread out; they go deep into the ground to anchor the trees. Some trees have prop roots that begin above ground to keep them very secured.

Roots can adapt to their environment. �Many plants have fibrous roots which look like little tree branches; helps prevent soil erosion and water loss. �Some plants have tap roots that grow straight down into the ground, so they are able to reach water deep in the ground.

Roots can adapt to their environment. �In tropical areas, roots attach themselves to the trees and take water in directly from the air.

Roots can adapt to their environment. �Storage roots store extra nutrients, like sugar, inside of them. �We eat many of these vegetables.

Plants and Animals Plant Parts – The Stem

Stems �Hold plants up �Support the leaves in the sunlight �Carry water and nutrients from roots to leaves

Stems �Most grow upwards, turning during the daylight. �Some grow sideways. �Every time the stem touches the ground, it anchors and starts a new plant.

Different types of stems �Desert stems store food and water for the plant to survive. �Small plants usually have soft, green stems. These stems usually die at the end of the growing season. �Large plants, like trees, usually have tough, wood stems. These stems can live for hundreds of years.

Inside the Stem �Most plants contain narrow tubes that carry water, minerals, and foot to different parts of the plant. �Xylem: carries water and minerals up from the root to the leaves. �Phloem: carries nutrients down from the leaves to the roots.

Inside the Stem �In soft stems, xylem and phloem are arranged in bundles throughout the stem. �In tough stems, xylem and phloem are arranged in separate rings.

Plants and Animals Plant Parts – Leaves & Photosynthesis

Leaves �Come in many shapes, sizes, and arrangements. �Most are very thin and flat to trap sunlight. �All leaves contain chloroplasts, which have a chemical called chlorophyll in them – used in the process of photosynthesis.

Photosynthesis �The process in which plants make food from the sunlight. �Photo = light; synthesis = putting together �Plants use water, carbon dioxide, and sunlight to make food (sugar/glucose) and oxygen. �Plants use some of the glucose that is made as food, and stores the rest as starch.

Photosynthesis

Cellular Respiration �When plants have to use this stored starch for energy, they go through the process of cellular respiration. �Plants take glucose and oxygen to make carbon dioxide, water, and food energy. �Humans also do this.

Leaf structure �Leaves have veins going through them, which hold the xylem and phloem. �When the veins are full of water/nutrients, the plant does not wilt.

Leaf structure �The upper surface of the leaf: upper epidermis. �Thin and flat; traps sunlight. �Has a waxy covering which helps prevent water loss; called a cuticle.

Leaf structure �Below this layer is the palisade layer, which contains tightly packed cells containing chloroplasts.

Leaf structure �Then is the spongy layer, which has loosely packed cells to allow carbon dioxide to pass through the cells.

Leaf structure �The bottom layer is the lower epidermis. �This layer contain several tiny pores, called stomata, that can open and close to allow water and gases to move in and out of the leaf. �Guard cells are located around the stomata, and change their shape forcing the stomata to open or close.

Leaf structure

Plants and Animals Non-vascular vs. Vascular plants

Non-vascular plants �Plants that do not contain xylem and phloem are called non-vascular. �These plants do not use tubes to move water and nutrients; instead, it just passes from one cell to another. �They are limited in size because they do not have structure. �Example: moss

Non-vascular plants �Do not have flowers, so they do not use seeds to reproduce. �They use spores – single reproductive cells that grow into new plants.

Simple Vascular plants �Like moss, these plants use spores to reproduce. �They also have two different stages in their life cycle. �Examples include ferns and horsetails.

Seeded Plants �Spores are not as successful as growing into new plants, so the majority of plants fall into two groups: gymnosperms and angiosperms. �Both of these types of plants use seeds to reproduce and form new plants.

Gymnosperms �Plants that have unprotected seeds. �Most common: conifers, or cone-bearing plants. �Pine trees, evergreens, firs, etc.

Conifers �Most conifers produce both male and female cones on the same tree. �Male cones produce pollen. �Female cones can be as small as 2 cm or as large as almost 2 feet! �They have woody plates, called scales, that protect

Plants and Animals Angiosperms

Angiosperms �Flowering plants �Grasses, herbs, shrubs, trees, etc.

Angiosperms �Pollinated by wind, insects, and other small animals. �Bright colors, shapes, and odors of flowering plants attract pollinators to them, and then the insects and animals carry the pollen on them.

Angiosperms �Angiosperms produce fruit that protects their seeds, including apples, oranges, tomatoes, peanuts, and acorns. �Keeps animals away from seeds and protects it in cold weather.

Plants and Animals Plant Reproduction – Gymnosperms & Angiosperms

Gymnosperms �Remember: the same tree can contain both male and female cones that produce male and female cells. �When these seeds join, they are able to produce new plants.

Angiosperms �In angiosperms, male and female reproductive parts can be found on the same flower. �The male parts make up the stamen and produce pollen. �The female parts make up the pistil and produce eggs. �We already learned that pollen can be carried by wind or pollinators to places where the eggs may be.

Angiosperms �Before a flower blooms, it is called a bud. �During this time, everything inside of the flower is covered by the sepals. �Once bloomed, the sepals look like green petals.

Angiosperms �Inside of the petals are the stamens, which are long, thin stalks. �A flower can have several stamens, and each stamen has an anther at the top of it that produces pollen.

Angiosperms �At the center of the flower is one pistil. �Most of it is a long, narrow tube called the style. At the top of the style is the stigma, which is sticky to hold on to the pollen. (pollination) �At the bottom of the style is the ovary, which holds the eggs.

Angiosperms

Methods of Pollination �Self-pollination: the pollen of one flower joins a stigma on the same flower, normally due to wind. �Cross-pollination: the pollen of one flower joins a stigma on a different flower; more common. �Cross-pollination allows for more genetic diversity among plants; Gregor Mendel used this process with his pea plants.

Plants and Animals Seeds

Seeds �Seed coat: outer covering that protects the seed. �Embryo: inside of the seed; a tiny plant that has potential to grow.

Seeds �Cotyledons: storage for food and water kept inside of the seed to supply nutrients to the seed. �Monocot: plants with one cotyledon in their seeds (corn) �Dicot: plants with two cotyledons in their seeds (beans)

Seed Dispersal �Plants are adapted to disperse (scatter) their seeds. �Maple trees have wing-shaped fruits that spin to slow down their fall, allowing the wind to carry them.

Seed Dispersal �Many plants depend on animals, like oak trees. Squirrels carry their acorns to new places and bury them.

Seed Dispersal �Some seeds have a rough covering called a bur. These stick to the fur of passing animals and eventually fall off.

Seed Germination �Seeds need soil, warm temperatures, and enough water to grow. �When the conditions are right, a seed will sprout, or germinate, and begin the next stage of its life.

Seed Germination �Step 1: take in water. �Step 2: the seed coat splits due to swelling. �Step 3: the root begins to develop. �Step 4: stem emerges and grows toward light. �Step 5: growing plant, called seedling, uses food storage to grow. �Step 6: leaves grow and use photosynthesis to make food. �Step 7: once the plant is growing strong enough, the cotyledons drop off.

Seed Germination

Plants and Animals Plants Respond to their Environment

Responding to the Environment �All living things respond to the environment around them. �A stimulus is anything that causes an organism to respond. �A plant’s response to a stimulus is called a tropism.

Phototropism �The plant response to light. �Caused by chemicals (auxin) that direct the growth of a plant’s stem in the direction of light.

Gravitropism �Plant’s response to gravity; caused by the pull of gravity on cells at the end of the roots. �Causes the roots to grow down and the stem to grow up. �Without this, plants would not be able to grow from seeds.

Other Responses �Some plants, like the Venus Flytrap and mimosa, respond to touch. �The VF closes its leaves to trap insects when they land on it; the mimosa curls all of its leaves when it is touched.

Other Responses �Short-day plants: need only a few hours of sunlight to grow. �Long-day plants: need many hours of sunlight to grow. �Day-neutral plants: can grow in any amount of sunlight. Song